Don't know about repairing siege but, yes you get AP for repairing walls, 27 AP per click I think (used to be more if you had a resto staff equipped, but that doesn't seem to effect it any more)
Taking resources gives you 25 AP, but if there were enemy players at the resource you will get more, like wise with keeps, the amount of AP you get is relevant to how many enemy players were defending but I don't know the base amount of AP for an empty keep.