Guilty of not reading the whole letter, but read some, and I get the sense you are brave, and thoughtful and passionate, all valuable qualities.
Wanted to give you some support. Some situations are oh so messy in life, some worth fighting for. You've decided to fight for this one to the best of your ability.
My own rule for myself is have I maintained my integrity in a situation and done my personal best? Sounds like that's what you're doing.