AF is right - you do have to be strong to deal with this. Unfortunately, it's a damaged, misguided form of strength. You are using all your strength to endure, endure, endure, and to deny, minimise and delude yourself. The effort and strength required is massive. The amount you need to start believing that you are worth better - that you are worth something at all - and should leave is actually much, much less, but the mental leap is harder due to the nature of abuse.
I have some other points you've brought up, OP, that I think need addressing:
You can leave for any reason. You can leave for no reason. The idea of having to have a big enough reason is bullshit, and can and will only lead to more abuse and damage, except to your child in the future, as well as you. Has it lead to less abuse so far? Of course not.
You wondered about the wisdom or fairness of leaving him if he never gets any worse in the future . My love, even if he stays at this level for ever, and never worsens, it is already a far too abusive and toxic relationship to be in. More importantly, even if he stays at this level, it is already a hideous one to bring a child into. Merely staying at the level he is will cause mental and emotional damage to your child. Your partner abuses you because of his damaged childhood - surely you can see that a damaged childhood for your own child will just continue the cycle, an abuser for a son or a victim for a daughter? You stay with him and you have to accept that you are choosing to have your child emotionally scarred for life.
The very fact that he would not you go means that this is a relationship you must not be in. Barricading the door is incredibly serious and a massive red flag. In fact, there are certain red flags that indicate sn abuser who is more likely to seriously injure or kill, and barricading someone in is one of them.
The begging and pleading then being wonderful for a few weeks until it goes to shit again are all part of the classic cycle of abuse. Your life with him will always be this way.
What if he gets drunk and decides he wants to kiss your sleeping baby? What if he digs his fingers in or twists their head to achieve it? That could kill them.
Why are you going on about trying to talk to him? It sounds like all you do is try to talk to him, try to get him to understand you and your pain, etc. the fact is, he doesn't care. You don't exist as a real person for him, he is only nice to you when it serves and pleases him. If he cared about your needs or feelings, he wouldn't abuse you in the first place. He keeps telling you he won't talk, isn't interested, won't listen, and the problems and blame are all yours. You have talked far too much, not enough. Every time you talk and he shuts you down and you stay and tolerate him and his shit, you actually do communicate very well then - unfortunately, what you're telling him repeatedly is that you'll put up with his abuse, no matter what he does. It doesn't matter what you say, because your actions tell him that you'll be his victim. Why should he listen to actual words when you've already told him what he wants to hear?