Hmm, he's very good at what he does, isn't he?!
He has somehow persuaded you that you leaving was because YOU are the horrid person and HE is the kind and faithful person, left behind.
But the reality was that he was controlling, using abuse, silent treatment and negging to get you to do what he wanted you to do. That didn't work because you moved away.
So he changed tactic ever so slightly, and kept in contact, gave you love and affection. But every now and then (and by the sounds of it more frequently lately) he is slipping up and the real him shows through, and he is calling you names etc.
Once he saw that he got you interested in 'trying again' he felt he had won, and changed tactics to gain the upper hand, and try to get you to start jumping through hoops to 'win him back' when all the way up to now he had been the one 'trying to win you back'. Clever, clever game playing by him.
This is not a kind, loyal, man. This is someone who thinks he can control you. And that's because you didn't cut all contact when you moved away.
And then when you start to think what he will be like around your son? That man will NOT want you supporting your DS in any way, shape or form.
If he gets his clutches on you, he will force you to make him the centre of your world. What he says goes. You will never be able to tell him if he upsets you with his behaviour. Any deviation from this path will be met with coldness, anger, abuse, silent treatment and any other form of punishment he thinks up. He will isolate you from your friends and family and when you are completely alone this is the type of man that will turn to physical abuse.
Do NOT move back. Cut off ALL contact with him. Get your clarity and self confidence back.