2 - Can't really help you. I do know from the small amount that I printed 6x6 on my 23C-II, I had the same problems. It was pretty annoying. I guess I was just making too small of prints for reasonable printing times.

3 - Is it a regular glass carrier? If so, maybe get a sheet of AN glass for the top. Should help with newton rings. Focal Point should be able to cut you a custom sized sheet if they don't stock the right thing already.