Things haven't always been rosey with my first XW. We've had tons of fights and our time in court. She's criticized my childrearing. But know what? I don't give a rip what she has to say about me or my parenting. And we don't hang out together...not like you do with Andy. I don't come in her house, sit down, and have tea. I come to the door and pick up the kids. I say "Hi" at the swim meets and sit apart from her. I exchange information about the kids as concisely as possible and get off the phone. We have a "tolerance" of each other and that's all I want. I just want to be able to see my kids and nothing more.
Isn't there some kind of Christmas break that the kids have? I'm not saying go all the break without seeing them, just split the holiday season in half and have the kids for half and him the other half. This year Xmas, next year New Years?
But I hear you. You got a lot of bad memories built up. But you need to think solutions, not problems, otherwise I don't see how you'll ever be free of Andy or able to start over. When everyone suggests something you say why it isn't possible or how there would be huge obstacles. It sounds difficult, but you have a closing window of opportunity to have a relationship with your kids. You will always be their mom and have a connection. My first XW saw her dad very very infrequently, far less than you, essentially nonexistent, until she was almost out of high school, but despite his absence from her life continued to want to be part of his life.
This is just my opinion, but I think the main stumbling block is still wanting to have a relationship with Andy. Being around him gives you expectations that you'll be treated like his wife. You get upset about other women because you still want to be his only woman. If you got to the point you didn't care about him, maybe didn't even like him, you wouldn't care who he was with. You might even prefer it because he might not be so stingy with the kids. I think life would be easier for you with him completely out of the picture. Can't you just say to him, "I want to see the kids for a day or two during the Christmas break at my place without you present. I just don't think we should do this pretend family and it doesn't really help me foster a better relationship with the kids. If you are so interest in 'doing the right thing' then don't include yourself in my plans." That would be like my first X saying "sure you can have the kids, just come over here in my presence where you are uncomfortable and see them." It's B.S.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt