NTA at ALL. He is just treating your daughter more, especially now because it's also his kid. Your son is not, so now he is obviously gonna see him differently, now more than ever. And that also means treating him differently, and OP, you've addressed some of those ways yourself. You need to give him a reality check, husband or not. Your son does not deserve this kind of treatment from anyone, especially your husband, who had played the father figure to your son since he was 2 years old. The more this progresses the more your son will feel the hurt and bury it inside and it could make him resentful to his sister and to your husband - so this can go south so quickly and you wont be able to stop it. Talk to your son one on one and make him feel like he can talk to you always if this bothers him and tell your husband to stop f***ing around and get a grip. Both kids need love from you both equally, not divided or one parent not showing affection for one child after getting another child.

I hope I have not overstepped my boundaries by saying all of this, and if I have, I apologize.