Actually, that is completely untrue. A teenager talking to you like that is confused, angry, and that’s not really surprising given what I assume he’s hearing from his dad, that there is a new baby, a new man in the house, and every other thing. You think about how you’re feeling, and now imagine coping with that at 13.
Just so you know, it doesn’t matter how your child appears to feel about you, if you kill yourself, they will be dealing with it for the rest of their lives. I’d actually go so far as to say that it would be worse if you have this currently estranged angry kid, because they will think they are to blame.
All you can do in this situation is keep firm boundaries, and keep loving them. One day he will see his dad for what he is. I’m sure you’re not badmouthing his dad, as you have seen the havoc it causes.
again, it’s too late now, but I don’t understand how, if you have these things going on with your older children, and alienation etc etc., you found the capacity to start a new relationship, and decided a new baby would fit in easily!! I’m agog, as any one of those things would be enough for me. On the plus side, all of this will move on, it simply cannot stay this difficult forever.
Oh, and on to your partner - I would not dismiss the idea that he is finding the baby especially hard work because CE can impact sense of self, masculinity, and of course the physical incapacity that he will continue to remember/maybe deal with for a long time. Even more reason for you both to work together, rather than him assuming the baby will just be fitted in to his requirements.
Maybe, and I hesitate to say this, because I’d usually yell at someone of this, but maybe you could consider unattaching at 6 months or so, a little, so that you can make a bit more space for everyone/everything else.
You can also explain to DP that this stage is temporary, you won’t be co-sleeping forever, and you’ve got the rest of your lives to get into a routine!