Obviously, the ideal thing would be for your H to morph into a decent, loving person. But since that's not going to happen, staying together will not be without its own effects on the DCs, as we talked about upthread.
Now, to answer your points:
Mummy, Daddy, DS will still be a unit to your DS. My 8yo still talks of mummy and daddy in the same phrase, even though she can't remember us living together. We're both her parents and we both love her. That's it as far as she's concerned.
Change will be difficult. The way to help him adjust is by having a very clear and regular new routine and making sure he knows what to expect. It will be hard for a while, but then it will become the new normal.
The nights will be harder, doing it by yourself. But all the advantages of not being exposed to his poisonous words will make that bearable. And at some stage, when the baby's old enough to do overnights, you should get some nights child-free and that's bliss. 
The children will not hate you. Change is a normal part of life, all the more for children. They are very adaptable. If you give them a secure, happy home and do your best to enable contact with their dad, what possible reason would they have to turn against you?
Loss of a relationship you thought you were going to have in the early days - that's hard. You'll have to grieve it. At the moment you're suppressing your emotions and that's really not healthy. It's not easy, the emotional rollercoaster, but it's the only way to move forward.
Maybe your H will get depressed. Maybe he will blame you. Maybe your DCs will listen to him and say something when they come back to your house. Then you will tell them that Daddy is an adult and he has to look after himself. It's not your job to look after him. If he really did stop looking after himself, they would feel safer with you and look to you to keep them safe with their contact with daddy.
Your thoughts just now are coloured by the way he thinks. That's how much his opinions have become part of your mindset. I remember how it felt to be surprised by small acts of kindness because they just weren't what I expected while I was with my H. You're expecting blame and hate because that is your norm. Time to rediscover your own opinions and abilities!