I think he has done an absolute number on you, to be honest. You're still viewing everything through a prism of how he will think, feel and react. Who gives an airborne fornication? What matters is that you support his relationship with the kids (increasing holidays and offering longer weekends when he has them enables him to see them as much, without adversely impacting on your own time with them) and your own relationship with them, too. His thoughts are his own business. Your kids need close and loving relationships with you both.
You barely see your own kids for any of the fun part of the week. The courts don't offer every other weekend or that plus more weekdays or 50/50 arbitrarily. They do it so both parents have the chance to nurture a decent relationship with their children. He's hogging the cream and leaving the skim milk, effectively.
Wheatus that cap is outdated. He should be paying £336 a week - just checked it on the CSA calculator - which is £1460 a month. Or, put another way, one and a half days of his monthly earnings. He's not "close to that" if he pays £800 a month, which is less than he earns in a day. I don't think £660 extra a month is nothing, and that's even after applying the CSA earnings cap! And if the Children Act (from memory?) were used in addition to the CSA, she might be able to get them more. He's a colossally high earner and his kids are getting peanuts, proportionately. And it's not as if he's in an income bracket where paying more sensible amounts of money would cause him hardship, either. He's just being tight.
OP, is he paying for school fees, and did you get a property settlement of any kind when you left? What sort of legal representation did you have, how independent was it, and did they talk about what you might be entitled to? I'm just scratching my head at how much of his own way this man has had and apparently will keep right on having. Why aren't you angrier? I'm honestly puzzled. What you describe in your marriage is financial abuse. You say you aren't scared of him, but you tolerated financial abuse, then left in a way that allowed him to continue controlling you, both in terms of your relatively awful financial provision, and the really inequitable contact arrangements. It's all on his terms. Why? Why talk about getting a tiny bit more of his earnings to care for his kids as "bleeding him dry" and don't you think that that is his mindset coming from your own lips, even after all this time?
I think you really, really do need to think about doing the Freedom Programme. You may be out, but you're still thinking along the lines he inculcated. You don't need to.