My BPD is mad that my l. sent him a letter to contact me only in writing regarding children. I had to set my boundaries after eleven years of bulling especially past several days. Of course he called me after he got the letter and texted and emailed he got the letter.
When he came to get the kids today, he barked at me that I need to pick up the phone because he wants to talk to the kids. I told him he can text me then I will have the kids call back. It happened one time last year.
Now he is saying he can't bring the kids back for Mother's day. I was willing to meet in the half way at the church on Sunday. 15 min. from his place.
His text " I can't. You can pick them up".
My text "If Sunday doesn't work out for you, please follow the contract and drop them off by 6 pm on Saturday.
His text "no thank you, This is my weekend. if you want to see the kids for Mother's day, you come pick them up".
This is not his first time trying this.
My sep. contract says husband shall be responsible during his visitation. My l says it includes pick ups and drop offs. I told my BPD that multiple times and he says he knows but it is not fair. Last month, he texted that he expects me to pick up or drop off one hour before he was supposed to pick up. I said that I am following the contract. So he texted saying that he is not coming to pick up the kids this weekend. It is such a shame that kids are put in the middle because of my laziness. My children especially my daughter was devastated. Broke my heart. Then the following weekend, he said his car does not work. a new car he bought during separation... .I knew it was a lie but I went to get them. Maybe that was my mistake. My l. told me that I need to draw a line and be strong. Honestly I do not mind going to get the kids but not this way... .he wants to get his way by pushing me around. He can get a lawyer and tries to change the term. He has no lawyers and got everything his way so far because of my previous lawyer's poor job and my fear for confrontation.
Now he sent me another text "My interpretation of the separation agreement is that I am responsible for my visitation. So that makes you are responsible for your visitation". I did not answer. I am willing to miss this Mother's Day to keep my boundary. It does suck with the fact my kids will spend time with his new girlfriend and her kids but we (me and the kids) will be okay. They (6+7 yrs) made me promise that I wouldn't open the presents until they come back.

I do not want to give in anymore. I called my l. to get advise. But she left for a day.
Is his interpretation correct? What would you do? How would you respond to his last text? or just ignore the text? Would I break any rule to ignore the last text? Please Help!