During the separation he lost his job and decided to pull the offer he had presented his then wife off the table since he was making more money then he thought he would be making at another job. He then went on for a year and half of not finding a job. So he did not move forward with the divorce. During this time he sold the house that they had lived in and thought that since they had alot of money from the sale since he was now renting that he could have her agree to taking a large lump sum of money even after splitting the money from the sale and be able to move forward with the divorce without having a job. she did not take this b/c she wanted to know how much he was going to make at whatever new job he was going to find. he finally found a job and for months went back and forth on trying to come up with an agreement on the money without going to court. Everytime she would not respond and he would say he was going to file and the day he said he was going to file she would call and say "no lets work this out without going to court" and again a month or so would go by and she would do the same thing all over again.
In the meantime, I was on the sidelines waiting to more forward with him. We had waited over a year for me to meet the girls. It was tough to date him when he didn't have much freetime and i was not involved with the girls but it was for the best. Now I am very involved with the kids and spend as much time with them as possible. But I am still not allowed to go to any events, games, birthday parties where the mom might come. I can't even be in the car when he picks them up and drops them off b/c the girls know that their mom will flip out. My BF says it's for the kids b/c she takes it out on them. If she gets upset she will go weeks without seeing them and makes it known what she is upset about. He says this will all change once the divorce is final. I will not move in with him until the divorce is final so that is another thing that would be a big adjustment for the girls.
He has asked their mother multiple times to meet me and she refuses and calls me all sorts of names and threatens that she "doesn't know what she will do if she ever sees me". This has made moving forward very difficult and caused many issues with me and my BF. I feel like he doesn't take my feelings into account and uses the "its best for the kids" to not upset the mother. So i can be as mothering as I can be and as soon as she decides she wants to show up I have to sit out.
I am so scared that she is going to be a constant battle for us moving forward that it gives me pause moving forward with him. He doesn't want to upset her b/c the girls get hurt in the process when she doesn't see them. I want to protect the girls but at the same time.. when do my feelings come into play?

This weekend is his 9 year old birthday. She asked me to plan the party and help her come up with cool ideas. I did and was so happy to be a part of it. Then I find out that the mom said she was coming (she has never stepped foot in his house) as long as i didn't and told the daughter that. She the daughter told her dad that she wants me there but knows mommy won't come if i am. So I have planned a party but i'm going to be home alone while the mom may or may not show up for her to blow out the candles and then leave. Obviously, this has caused a huge issue with my BF and I since I feel like at this point he should not let this happen. But he says its for the kids and I should understand.

Am I wrong for being upset? Is it crazy that this is still going on after 3 years? Will he actually change this once he is divorced? I love this man and his girls more than I ever imagined possible but I don't know if I can always be the one that gets hurt.