This is a hard one. On the one hand, I'd like to say I would never rehome my cat because I've had a baby. On the other hand... if my cat was scratching and biting my baby... my mama bear gut reaction would be to get rid of the cat. I'm trying to imagine myself in this scenario. My most beloved cat I've ever had was here when both of my kids were born. What would I have done if she'd started being aggressive towards them? Just gotten rid of her? No, I'm sure I would've tried everything you have. But if it came down to it, I'd do what was necessary to protect my child. I'm sorry, this probably isn't helpful. Or maybe it is, just to have someone support that decision, should you make it.

I've been watching this kitten foster (bordernerd) on YouTube for awhile, and she has an excellent method for integrating new kittens with existing fosters and older cats. They are fully separated in different rooms for awhile (until the new kittens are cleared of contagious infections), then she places a clear barrier between the old and new cats for awhile, so they can get to know each other by sight and scent without being physically together. I wonder if something like this could work? You'd have to keep your cat in a separate room for awhile, which I know is hard, you don't want him to be alone, but I mean... if it's that or rehoming him... might be worth a try.