First, you're spot on when you talk about the hypocrisy of anyone referring to a trans person's transition as selfish. What is selfish is expecting us to go on living a life of pain every day just so that they can feel better about who we are and their relationship with us. My wife has never come right out and said that but she's hinted toward it and I've gotten the question from others. I simply point to the fact that if I hadn't started transitioning now, with the suicidal thoughts I was starting to have, I don't believe I'd have made it 5 more years. So my wife would have lost me, my kids would have lost their dad, etc. Sometimes putting it in those terms opens some eyes.
Regarding the guilt trips, that's pretty common too (even without the bipolar disorder complicating it all). Do you guys see anyone together (therapist, counselor, etc.). I've found with my wife it's good to have that mediator their to keep both sides actually listening to each other and not cutting each other off. That cut you off to respond behavior is a sign of someone who is listening to respond rather than listening to understand. That has to change if you guys are going to make any progress.
Sounds like you're doing all you can and I'm glad to hear you have support. That's so crucial. Keep your head high, you're doing great!