'What's best for the children' will form the basis of any legal determination about access arrangements. It is highly unlikely that anyone would deem more time with him than you as being 'best'.
It sounds like you (OP) are already using this principle in your decision making and he's not.
It is obvious that he is hurting, is angry, blames you and is wanting to punish you. He isn't acting like someone who is trying to make it as easy as possible for the children. This isn't going to help anyone.
My work often involves supporting family members in these sorts of circumstances. As previous posters say, the most common outcome when family dynamics share the history you describe, is that of the father reducing and reducing their contact as time goes on, even when they fought tooth and nail for 50:50 or more.
Often, fathers enjoy facilitated and non demanding parenting that comes with being in a family unit where the mother does all the heavy lifting. Having sole parenting responsibilities whilst accessing one's children isn't the same. Sadly, this tends to fuel further resentment and blame towards the mother and reducing time spent with their children.
It's important for you to hold on to the facts that it is entirely reasonable for you to end the marriage, whilst it isn't easy for children - they can and do cope well with divorce, he needs to come to terms with the situation through accessing support (informal or professional) from people other than you and your children.
I'm sorry that all of you are having to through this. It isn't something anyone chooses, but it's something many people have to face. It sounds like you are navigating it really well, despite it being so difficult.