What a burden! I would pray for him, ask St. Monica and St. Helen for their intercession (both were women who prayed fervently for their loved ones’ conversions), and continue to invite him to attend Mass with you. If he says no, then don’t push it. Same with RCIA. You can also try to come home and say, “wow, listen to what I learned today that has touched me, made me understand more, etc” He may not take it to heart, but just being excited about it and sharing in non-threatening ways can plant seeds in his heart.