okay so you do have options, that's good, I'm glad you have put your name down on the waiting list.
I just want to make some comments about sexuality - when you call yourself cis, that is an indication you are spending time with transgender people. For a straight female it's simply unnecessary to say cis, isn't it? That concept of not being comfortable in your skin is a transgender issue not a straight one.
Secondly your partner is still one person, still got two arms, not four, still got one brain not two despite the inconsistencies that make him feel female it's still one person in charge of one body, one person who decides what dress to wear.
And one person who lied to you from the outset of your marriage just as the first man did. Their sexuality develops with age like we all do but it doesn't change. They always were same sex oriented. From what I have seen it appears declaring yourself a lesbian to your wife is a recognisable stage in the world of transgender but it doesn't mean he is actually attracted to women.
tbh I don't believe he has been faithful to you - I just think oh okay he retired, less opportunity - and so I tend to think of the appearance of online accounts etc as a grooming technique - softening you up by degree to accept him feminising.
what I do believe is your instinctive response - feeling betrayed.
You sound like a very nice person - this is typical of us straight spouses - nice friendly empathetic. So I am glad you have your own space. I had been with my ex from the age of 19 and it was a shock to discover he was gay in denial at 57. I had my studio, it was a real retreat being at the end of the garden and already I spent an increasingly long time there so that my friends had stopped visiting me In the house and visited me there and eventually I moved my bed in and from there I got a divorce and moved out.