Hi EJ,
Just saw your post! New adoptees are always a bit skittish, some like your male, may take a little longer to get his bearings.
Let him hide if he wants to but always make time to sit with him, try and play with him, and let him get accustomed to your soothing voice. Eventually he will become a little more adventurous, and will come out of hiding. Just do not force him to go out in the Big World of your entire home. Keep him confined to his little space with all the comforts he will need....and of course you by his side.
Cats are very territorial and especially males so he needs to establish HIS territory in order to feel in control, and I am sure that will happen.
All he needs now is You're Love and attention.
Keep us posted ---we now share in your experiences. This is how we learn.
CML
I've never had much luck with Feliway, despite the fact that people swear by it. Try giving each kitty its own space, something small like a bathroom, with own litter box, food and bed.