Its a horrible situation for you and your child. I think I agree, if he is going down this path its hard to see what alternative you have. Wont he want to still see your son though?
Its hard to see how he is closer to God after doing this, I cant see how he could possibly think that God wants Him to have his body cut about and act as if he is female, let alone commit adultery with men! Sadly people will try and justify what they want to do.
So sad that he was so damaged, but in a sense he married you under false pretences as he must have had an idea of all of this then.
I know a young lady whose husband is going through this 'changing into a woman' process, they too are getting divorced. The small child now thinks he has 2 mums:-( I also know another lady whose dad left her mum for another man, its not as uncommon as some may think.
Yes forgiveness and praying for him is very positive.