I was honestly made to believe that it was harmless that I need to pay him more attention that I am the cause of his problems.
You see how everything works in his favour, right?
How he blames you for everything, even poor sleep?
Yes, leaving is easier said than done.
But it boils down to what you want, and whether the way you have gone about getting that has worked up to now, or whether his responses have basically been an insult to your intelligence and an expression of contempt for you on his part. Which is what you have got.
So forget sitting him down and telling him how all of this is making you feel. You have tried that and it has got you nowhere.
The reason he is doing this is complete, total inadequacy as a man. You can't make him change. Give up any hope you have that you are special enough to him to make him give up what he is doing. He won't change. This is who he is. This is what he does. The thought that women are fighting over him makes him feel important. If he didn't have that there would be nothing in his sad, pathetic little life. A good woman and a lovely baby are not enough and your love and commitment are things he neither understands nor values.
Look up the definition of gaslighting. Essentially it means taking absolutely no responsibility for any hurt or damage he is causing. Do a bit of reading about the sort of man who does this.
Make plans to get rid of him. Show your children an example of a strong woman who doesn't let a man treat her like shit.