Re: rear sprockey alignment
Is it wobbly side to side, or "out of round"?
I have used a hammer to make them straight once tightened down...it was the only way for one I built. I just whacked it "smartly" a few times to true it up, as it was the sprocket warping, not tan alignment problem.
If you are having trouble centering it on the hub, slowly tighten your bolts in a cross pattern like you would do the head bolts, or the lug nuts on a car.
Some of the sprockets are drilled off center (good luck if that's the case).
If it is out side to side, just slightly, I would let it go. If it's running off center, you have to do something or the chain is continuously tightening and loosening and that causes all kinds of problems.