write or wrong: I’m just thinking back, and I remember what allowed me to give Judaism a chance again. I had all these ideas that my parents cared more for their status than for me. Sparing the details, it took until I realized that my parents would literally do anything for me, as a person, before I was willing to consider anything about their lifestyle. You say you try to make his favorite things. Keep it up! It was those actions which allowed me to open my eyes and consider being religious.
He will come around. Be natural and loving, just not too much that he sees through it as ‘just another kiruv tactic’ nor that his siblings be jealous. Just make sure he knows that it’s him you love and you want more than anything for him to be happy and he’ll come to realize (without you telling him) that Judaism leads to the most fulfilling life.
He is judging Judaism by the Jews. You need to show him how beautiful and essential Judaism is and how genuine you are about your commitment to the Mitzvot and to your fellow Jews (ie your son, regardless of his dress) and he’ll realize for himself the beauty of Judaism.
I apologize that I wrote this choppy; it’s late.
Hatzlocha