Well, not using your ult is a problem you'll have to fix. IMO you'll want to use an offensive ult 99% of the time you use one, e.g. Incap, Soul Tether, or Dawnbreaker of Smiting. This is central to killing players.

I don't know what you mean by "jumping". Actual jumping is not a requirement, especially not on a stealthy NB. If, on the other hand, you mean Shadow Image, I would say that's optional. It is a fun and useful skill, but not a must have in all builds. If you mean doge rolling and line-of-sighting, that is generally a must learn for all PvP builds, including nightblades.

As to getting way too close, you'll have to be more specific about your playstyle. If you are a melee ganker or bomber, you will of course get close, usually in cloak. Statistically speaking, the risk you take in cloak is relatively low, but depends heavily on the target(s). Once you're out of cloak, your playstyle could differ vastly:

• As a traditional stamblade / ganker, you will probably use melee skills, such as Concealed or Surprise Attack, melee heavy attacks, and a melee execute. In other words, you'll stay in melee range and probably dodge roll a lot. Your approach may be to overwhelm your targets by doing very high damage, while being squishy yourself.
• As a magblade, you may go in close for an Incap Strike, but then back off and try to kill the target from range, e.g. since Swallow Soul / Crushing Shock are both ranged, and so are Merciless Resolve and Impale. This is my playstyle.
• You may of course be a bomber, which is a speciality unto itself.
• You could be completely ranged, using Crushing Shock / status effect procs, or a bow build.

That said, if you play Rallying Cry that makes you somewhat tanky, so maybe you're wanting to play a Brawler? I don't know if Way of Fire is that good anymore. Do you use Shadowy Disguise or Dark Cloak? Do you play around with Shadow Image?

It also depends on where you play. BGs? Ravenwatch? CP Cyrodiil? IC? Is your objective to survive and bring Tel Var home, for example.

I've come across nightblades who are tanky. I can only imagine that they run one or more pieces of heavy armor, along with more medium than light, that they run Resolving Vigor, that they make sure to have Shadow skills in their rotation (Surprise Attack / Concealed Weapon) often enough to keep their resistances up. Perhaps they run Dark Cloak, although the passive crit % from Shadowy Disguise on both bars is IMO hard to beat, these days.

I run a light armor magblade for the magicka cost reduction, e.g. cloak sustain. You are fundamentally squishy on such builds. Especially your physical resistance is extremely low. I don't like a Rallying Cry back bar on my build, because it does too little, too infrequently for me, in my context. I run a Wyrd Tree back bar instead, which means that when I decide to Shadow Image or cloak away, I may clear all DOTs, Curses, and so on. It plays well.

The other defensive piece I use are the Esoteric Greaves (only in CP / proc campaign). This will only work on magblade and, honestly, you don't want to use Vigor and you want to keep your dodge rolling and blocking in check, all while using double-regen food exclusively for the Greaves. So the playstyle is: "stay on the attack / brawl a little bit longer" than you otherwise could, but watch your stamina and disengage when you must. The greaves also serve as gank protection.

I do wear Balorgh while my front bar is currently Soulcleaver. With all the new dungeon proc sets, this is not likely optimal for ganking or PvP in general. However it is well-suited for Imperial City, my favorite place to play. When you solo a boss, you want to heal from damage and keep your health up, lest you get ganked. Swallow Soul, Sap Essence and Healthy Offering are all on my front bar.

For what it's worth, I'm an open world / CP Imperial City magblade main, specialising in the PvPvE combat of that place. This is my current build:

https://en.uesp.net/wiki/Special:EsoBuildData?id=617035

A slightly older version of the the build in action:

https://www.youtube.com/watch?v=NuTHJyFGo9Q

Farming an IC boss and getting ganked:

https://www.youtube.com/watch?v=hBdLIeihspY

Just a comment on that first video. This is basically a 2v2 turning into a 2v3. You may notice that, when the opposing DK leaps in, I take hardly any damage. This is an example of the Esoteric Greaves doing their job, but also of the DK running a very tanky, low damage spec. When the third blue player joins, note the blue flame above their head. This is their Sea Serpent's Coil activating. That mythic causes them to be snared, but do ~15% more damage in return. Players who can live with the snare and use that mythic usually know what they're doing. It's a sign to be careful and, indeed, I took a lot of damage after that player appeared. I had Healthy Offering on the back bar at the time, which meant I could block with 1H+S and spam that heal. That is how I outhealed the damage back from the brink.

It was very borderline. With my current build, I probably would have died, because I now have the heal on the front bar and don't have the same block cost reduction and mitigation while using that heal. You play a light armor nightblade with high cloak sustain, like I do, you're fundamentally playing a damage avoidance build, not a brawler build that stays in a melee fight for long periods of time. I chose to upload the above video to show how far you can push, but perhaps that gives the wrong impression. You can't have everything. A high cloak sustain magblade synergises with speed and/or Shadow Image. You want sustain, speed and damage. Tankiness, especially against physical damage, is left on the table in my build. The Esoteric Greaves are my only protection. They are powerful, but finnicky. You can easily misjudge your remaining stamina, for example. If you square off with players that are built for melee brawling and you do it on their terms, e.g. you stay in the fight too long, you will only lose in the long run. My playstyle is, thus, based on speed and weaving in and out of combat first and foremost.

This has been the best compromise for me personally. Shadow Image, but also just Shadowy Disguise combined with speed, are very powerful tools. On the one hand this is beginner friendly. On the other hand, when you actually enter combat, it is more demanding than a plain tanky build. The playstyle is also not suited to playing in high lag.

Honestly that build looks competent. It's not how I play, but I think it's how an experienced nightblade brawler would build, down to the CP and everything. Very balanced.

Best way to learn is to duel against different people at or slightly above your level.

If you want some easy successes, then playing a ranged build, or possibly a melee ganker, may be a better option.

If you want to survive, farm Tel Var, and do what you can in a sort of non-committal way, then my build is good.

The build that you have, being a brawler, won't have the outright damage to finish people off quickly, nor is it as inherently safe as playing ranged and cloaking away when someone gets close. A brawler spec means you need to have a brawling / duelling mindset. Brawls and duels ebb and flow. A "tanky" PvP setup doesn't make you passively tanky like a PvE tank, unless you build an outright "troll" tank with no attack potential. You need to work on your defensive rotation to "tank" people's damage, and you will have an attack rotation that needs to be more elaborate and flexible than a ganker's, because you lack the element of surprise nor do you have the same damage.

While your opponent's health is low, and they have no ultimate, e.g. they have just spent it, you are reasonably safe to stay on the attack. However, fights turn. Suddenly you may feel that you are being "focused", either because multiple, organised players are targeting you simultaneously, or because your single opponent is fully buffed, with full ultimate, and confident to go on the attack. Always watch your health bar. You need to learn to recognise those phases of a fight quickly and go defensive when needed.

You got an ice staff in your build for blocking, and you got your heals on that bar. Dodge rolling, line-of-sighting, and cloak are your other tools. However, the only way I know for you to hone your judgement is via duels. Duelling the same, slightly better person repeatedly for a while allows you to experiment with different approaches against a consistent opponent. This is important. Open world is very deceptive. You can be beaten down by a single, better player, while killing multiple weak players in the next fight. That's not you improving. That's just the randomness of open world.

I suppose I should mention that, on PC EU, you will find duellers at the Bergama wayshrine in Alik'r. It's probably the same on PC NA. The area is flat and featureless, which duellers prefer. That said, don't go there. It is a brutal place where the best players match up against each other. On second thought, if you are a really competitive person, go. Otherwise I recommend duelling with friends. The problem duelling very good players is that they will steamroll you. It is very difficult to get your bearings and learn anything under those circumstances, unless maybe they're willing to talk and teach.

My experience with good duellers is that they have very good mouse control and will play super-aggressively, always on target. Attacking skills, by and large, cost half as much as defensive skills, e.g. heals and shields. A player who gains the upper hand on you, staying on the attack while you hang on for life, will basically run down your resources and beat you, unless you are an outright tank. The trick is recognising when their burst is over, their ult spent, their buffs are running out, and you can go on the attack yourself. That said, a better player may seem relentless.

Edit: Also, the game is rock-paper-scissors. You may run into an unfavorable matchup that heavily favors one side, based on your builds alone.