AuroraMoon,
I'm so sorry that this therapist betrayed you in that way, and added to the pressure you feel from your husband. That would be my last session with her, and I'd report her to the practice for unprofessional behavior. (Plus, she may have rationalized her decision to stay with her spouse by telling herself that "sex when 'older' doesn't matter" but lots of women her age and older will tell you that's not true for them!)
In your post you lay out what your husband says about how he feels. He seems to be accusing you of quite a lot, projecting his own fear, hesitation and shame about his gender identity and presentation onto you, making you into the gatekeeper or gender police that "keeps him" from his preferred behavior and expression. He's displacing onto you the responsibility that is his, because he doesn't want to experience any consequences for what he wants to do and how he wants to act, and hiding behind you because he's too afraid to live what he says is his truth. When he says "a part of him would like to separate" believe him; when he says he doesn't want to because he loves you so much, and then accuses you of making him feel unsafe, unloved, etc, he is engaging in emotional blackmail.
What I say is that it's how you feel that's important.