For number 2 the latest sex scene allows for MC to apply light CBT to her partner. I realize it was tied to foot fetish stuff and players may like one but not the other might have missed it. I will try to avoid introducing multiple fetishes under a single choice like that in the future. For most fetishes they are split into done to MC or MC doing to others and even then you still will be prompted if want to do so with a certain character.
To answer 1 and 3, I'm straying to the lighter side of CBT. Anything done will never break the skin or have the potential to either. Nor is the sole objective the pain itself. So stuff like squeezing and stepping that is slow, sensual, and controllable, but nothing equivalent to a strike. Anything sharp will have to be relatively tame like teeth. Other objects like knives, scissors, and spikes or threatening the partner with an object is a no.
I hope that fully answers your questions. Thanks for playing!