1. It set the width of the prompt/value/comment" table. This is not the same as the border though, so this width does not set the width of the border. (That would have to be done via CSS, and because each form is different that would take some effort.)
2. I suspect you don't have the latest build, since this was changed in 4.31 PR14. Prior to PR14 it was ignored for drop-lists, but now you can set it explicitly in Pixels.
3. Not yet, but I'll try and add one in.
4. yes it's controlled in CSS, but there should be no difference between a button column, and a text column. I'll test here to see if I can duplicate.
Cheers
Bruce