For the Vampire Perks, you'll probably want to look at the wikia
page if you haven't. Between what I remember and what I read from it, you have to use the Power Bite in melee mode or the Drain Life in Blood Magic mode to "feed" while in Vampire Lord mode. I can't remember if it has to kill them, or if you can do it multiple times to one person before killing them, but I think I just went from city to city doing it till I got the perk (on a seperate save).
For the second part, did you get the Kindred Judgement
quest? I think the page says there's a bug where you may not get the quest. And if you did, you only need to go to Isran if you took the Dawnguard side. If you are with the Dawnguards, it could be because you are a vampire. You may need to cure your vampirism (on a separate save, if you want), and return and see if it works.