It’s wonderful to hear your trying to be open minded about it.
There is a huge range of reasons for men to like crossdressing. I believe the least of your worries should be that he is gay.
Our reasons for enjoying it is very complex and quite embarrassing to try to explain to the woman we love.
If his crossdressing is just the pleasure he gets from wearing silky lingerie then let him. It’s just clothing!
Speaking for myself, wearing silky lingerie in the bedroom with my wife is a big turn on for me. My wife has accepted it and has told me “It doesn’t turn me on, but it doesn’t turn me off either” I really believe our sex life has been enhanced by it. I know what it has done for my sexual experience and in turn I always make sure I am doing everything for my wife that pleases her.
Crossdressing for many of us men is fun and exciting and it harms no one. We do not do it to compete in anyway with your femininity.