THINK ABOUT YOUR KIDS
What do you think you'd advise your daughter to do, if she was living your life? If she waved her kids off to their father because they weren't compatible with her boyfriend? If she had a 12 year old wetting the bed in fear, and a boyfriend humiliating the child and saying he'd have to wear a nappy? What would you like your daughter to do, if she was living your life?
What would you expect a woman to do, if your son was treating her and her children like this? Would you be surprised if she left him, not for a week, a month, but for ever? Would you defend him, would you say oh, he gets stressed, he just wants everything to be lovely?
So poor Diddums says he's been crying. My heart bleeds for him... not. What a bloody sick, cruel, manipulative ABUSER. OP you have to let this go. He has no place in your life, no place in your children's lives, and if you get out now, for real, for ever, you just might have a chance to repair the terrible damage already done to your young son's confidence. I'm surprised your boy's father hasn't knocked your boyfriend's lights out (I don't condone anyone hitting anybody, adult or child, ever, in any circumstances, but my god I'd be tempted).
He can cry - good, but I bet they're crocodile tears, whining for sympathy. All this is your fault, see, he's trying to turn it round to make excuses for his horribleness. He's twisted, awful, maybe he needs 'intervention' but bad people don't come good. And he's bad.
Let him cry to his mummy, run for the hills OP, and hug your kid tight as you get yourself and him free of this monster.
You're worth more, and you're stronger than you think you are.