Last year I had to wait for him to make a decision, he was either going to go through with the marriage or our relationship was going to be over.
From all that has been said, and the indication that his testosterone level is normal, it seems very much that he is living in denial. The question is, is it a denial of being transsexual or a denial of being asexual, or both.

For example, his hesitation regarding marriage. Seems as though his inner woman was causing this hesitation, and his denial won out in the argument going on in his mind. Or he had issues with being asexual and worried about committing to a relationship that normally involves sexually satisfying one's wife.

Another example is his need to wear a skirt and panties before having sex. Seems he is not comfortable with having sex, as a man, and the clothes he wore let his mind, as much as possible, take "the him" out of the equation. Or it took him out of the equation altogether, mentally, and he made believe he was someone else.

His religion (same as mine) was quite possibly a crutch to avoid sex, as a man. Or an excuse to avoid sex because of his asexuality.

You mention porn. Was this an aid, a need, to him getting aroused? The mind is a powerful tool at times, but sometimes it needs help to get past an inner issue, whether it is being (apparently) transsexual or asexual, or both.

Hopefully his therapist is considering all the above possibilities.

If I were a therapist, and knew what the heck I was going on about, I'd lean more to the possibility that, gender-wise, he's a CD, and sexality-wise, he's asexual.