One more thing to note. Based on most others here, and those of myself to my wife.
He is totally in love with you, cherishes you! You are everything to him.
Dressing DOES NOT replace you! You guys will have to figure out how it fits into your dynamic. Some wife's participate, others know it happens, and give them space.
Chances are good that he does not want to transition to a female full time. For many of us, it is a part time hobby. But best get him counseling, to see if he has gender identity problems.
Chances are good that he doesn't know the answer to any of your questions, but he wants to give you comfort.
Chances are, he is scared about his own future. I myself fear that I am headed down the path of transitioning. Though I am 98% sure this will only be a part time thing, contained between my wife and I.
This is something you two can cope with! Make sure he knows that he can be completely honest. That's the only way it's going to work. He is dealing with years of shame, guilt, denial. It's going to be hard for him. At the very least he needs to be honest about his own feelings, and wants going FORWARD. No sense dwelling in the past for either of you.
You feel betrayed, but be clear that he wants to be with you. This is complex. You will both be figuring it out at the same time.
All the best,
Candice