For the asymmetrical limbs, I think the best way to fix it is to add more sinew to one limb to balance it out. Of course, tillering it correctly can get the limbs bending equally, but the sinew would make them both start from the same place, if you get what I mean. That would also mean extra drying time, though.
On tillering with the reflex, yes, it can be tricky. The f/d curve is a usually a bit different than a straight bow, so it'll seem like it's heading for too high a draw weight, when in reality, it's going to be too light.
1/2" for the tips is leaving plenty of room and more than enough strength. You could add some sinew wrapped nocks, but it's not necessary for strength.
For that style bow, it was common to have two side nocks on the bottom, and one on top. Not pairs, just one nock on one side of the bow for the top, and two (one pair) for the bottom. There are other ways to do them, of course, but that's how I usually do mine when working on a plains horse bow.
Sean