Reading some of these posts, it amazes me that some can read what the OP wrote and not "see" the "working out" that this couple has engaged in.... Good for them.
They were separated for 18 months and she agrees they should get back together and try again. He offers a "nudge, nudge, wink, wink" solution where they both understand that they are both trying to get something they want - on the way to getting what they want together, and they start the process of reinventing their relationship.
He offers a "this might work idea" and she suspends disbelief, understanding that he's working around an issue to address all their issues.
"Heck", both think, "If that's all it takes, this might work."
Been there, done that.
What adults work out in their private lives is up to them. She agreed to the entire ball of wax when she heard the pitch - she didn't call "Foul!" - and so far it's working out for them.
Great.
He just needs not to screw it up. Which might be hard to do since she's OK with it so far, they're talking everyday, and, both seem happy enough to be back together again.
Crossdressing is not that big a deal. Feeling awful about it, not talking about your feelings about yourself, and, hiding something that could hurt your SO, is a big deal.
Find a way to be OK - and be OK.