OK - IMO your creating a bunch of unnecessary drama for yourself by trying to hang on. Let's use haircut.
I could give a flying fuch how my XW cuts our D's hair.............she could shave their heads and if they laughed about it and thought it was funny who cares. If your S wants his hair out of his eyes then he needs to tell his mother. If his mother chooses to go a different route and it is in his eyes then your S needs to tell his mom. If he is old enough to complain to you about it then he is old enough to complain to his mother about it. When my D's complain to me about their mom I re-direct them right back to their mom.
Making the comment about buying a bed and not a power wheel. Not good........your jabbing her and it shows she still has you by the sack. It is weak and needy behavior.
You can go back through your sitch and read everything people have suggested to you. It is way too long for me type out.
Lastly......and I am not trying to be a fuching jerk. There is a part of me that thinks you like the attention. You have threatened to leave the board twice......then when people jump in you stay and that gets your conversation on your thread going again. It happened yesterday as well when AS chimed in. It is kind of the same thing that happens with your W. You have no interaction, then I don't know what happens and you have this conversation and needle her to get a rise out of her. It's like you can't go without getting attention.....like something always has to be stirred up.
You start to take your power back by not engaging with her.