From OP:
He is jealous and possessive. - Jealousy could be a misunderstanding, possessive is a strong word and implies more controlling behaviour. OP is afraid of him seeing if she leaves the house despite the fact they have now split up. That's not normal. How many of your exes are you afraid of being seen by?
He has lied about being infertile, presumably with intent to make her pregnant - if it was just about having sex without condoms, why not suggest she went on the pill? Okay, he could have thought he was infertile, but still, why not suggest a back up method just to be safe?
He is irrational to the point that OP can't have a proper conversation with him. He is refusing to handle this via legal means as it's clear they can't discuss the matter between them - okay, it might cost money, but seriously, what price is being able to see your child worth?
OP finds him "intimidating" and is "terrified of what he is capable of".
OP by contrast is keen to do the right thing by her child, whether that's allowing access to its father or keeping the father out of its life. She has no irrational dislike towards men in general, as she states she has a stable arrangement with her other children's father. Yes she was foolish not to take extra precautions in the relationship, but there's no point berating her about that now - I expect she knows it.
I'm sure I'll have x-posted but it seems clear to me who is being unreasonable here.