Colditz, I think you need to start thinking of DS's happiness beyond the next hour or day!
What we are all struggling to grow (IMHO) are adults capable of independent living who can form loving and close relationships with others and in the fullness of time raise their own children to be happy and contented.
I really don't believe that your current set up is going to give your DS the role models that he needs to have even a chance of achieving that
At the moment he is watching and learning from a totally dysfunctional relationship. His adult hood may be to treat women in teh way he has seen you treated. Or should he reject that, to be terrified of forming a relationship for fear that it will be abusive towards him.
He will learn to be feckless and someone else will pick up the pieces, slobbish, uncaring, foul mouthed, I could go on all night.
The point is, that if you look beyond tomorrow, this is doing your DS no favours whatsoever! It is totally the reverse!
I can understand your reticense to deal with this right now, but you need to be laying the foundations for a life without him right now. The early weeks with a young baby are incredibly stressful as you know, I doubt very much whether your relationship has got the staying power to see you through those weeks.
I wish it wasn't that way, but I really do fear that it is