1) That is a scripted vanilla event and not tied in to the fetish system at all. Unfortunately, altering that to tie into the system would be a huge chore and probably break a lot of things. Maaaaybe one day.
2) I'll keep that idea in mind
3) If you get a screenshot of the issue I'll definitely take a look at it.
4) There used to be a system (in vanilla) to abuse via the Talk system, but all of that was replaced by the Interaction menu. That is where you can torment/torture to your hearts delight, I think the other is just a description from before that change.
5) That description was just a quick "Lets get this thing released" and works off swollen level and not location. It will be fixed in a future version.
6) This one is a weird back and forth issue. I had the system set to stretch fairly quickly and (possibly) accurately, but the primary complaint was that every character was ending up stretched and torn. I drastically lowered the amount that someone will stretch per encounter for popular request, however left the setting as an option in expansion.gd (near the top, under settings) for you to be able to manually select your chance of stretching. The values are: stretchchancevagina = 50, stretchchanceanus = 50.