Those are excellent questions and points.
I’m certainly not an expert but will share my experience.
My SO learned well after being married of my ‘other’ side. It was supposed to be a kept secret. But, since we are only as sick as our secrets, I shared it with her. Here today, more than 10 years later, I am not sure if that was a good idea. We’ve been out together and the like. Still, there is an air of discomfort.
For you, I can share my SOs feelings – initial or otherwise:
1. Is he gay? (no)
2. Does he prefer boys to girls? (no)
3. Would be prefer to be this all the time? (well, I could be talked into it. I frankly enjoy being able to be both where it helps.)
This where you have to determine with him – I think – what drives him and why.
For me personally, CD has been an ‘all my life’ thing. It didn’t change my sexual desires. Just the way I wanted to present myself. I, too, am tall (not that tall but still tall) but still have that desire to feel pretty.
I think you are right to say this ‘why should his wearing a dress make him any less of a man?’ It won’t make him any less of a man. Clothing is clothing, right? Well, sure, but…
When it’s just the two of you, fine…but there is a big world out there that doesn’t have quite the same understanding as the fine people in this forum. This starts with immediate family, friends, neighbors, etc.
For the SO – particularly the genetic girls – it becomes a challenge to understand it all, explain that to others, potentially integrate it into your like, and finally, to ‘defend it’ – if needed. That’s a tall ‘ask’ of anyone.
Again, not an expert but sharing my experience.