Hey Ash. Thanks so much for sharing. It’s really clear in your post that you are struggling with a lot right now. I wish I could give you a simple answer.
My piece of advice is to seek out a marriage counselor to help you both work through these challenges. Be sure to look for a counselor that has experience with LGTBQ+ couples. My wife and I have been working with a counselor for some time and it’s given us a safe space to express ourselves and be heard. Be warned: it may not produce the end result you want so you should be prepared for that going in.
It sounds like you wanted to be open, accepting, and supportive but when faced with it found it really challenging. I get that. We all imagine how we would react in certain situations and are often surprised with the results when it really happens. It’s seems like your struggling with some disappointment in yourself as well.
I’m no expert and it sounds like you’ve done some research which I applaud. I can speak from personal experience that dealing with gender dysphoria is a significant cause of stress. Adding other stresses like work and family can make it worse. Being able to express yourself, express some amount of authenticity, is a huge relief. But the act of expression can often compound your self-hatred especially when those you love see it as shameful. And unfortunately telling him that you don’t mind if he does as long as you don’t hear about it is a clear message to him that you find it shameful.
Regarding his coming out to your adult child without your consent, I totally get your sense of betrayal. Your feelings are legitimate and real and deserve to be acknowledged. This is your child after all and his coming out affects you both. On the other hand, this is his secret to tell and he was sharing it with another adult who he clearly has a close relationship with. On the surface what he did wasn’t wrong, but it was inconsiderate as you are both part of this relationship. But, I obviously don’t know the details and may very well have done the same if I was in his shoes. Who am I to judge?
Please find a counselor to help you both work through these issues. There is light at the end of the tunnel if you are both willing to work at it. I wish you both the best.