Boundaries when being manipulated?

Hi coach!

Could you please share insights on how to handle (what feels like) manipulation?

Situation: ex, father of my 2 kids. Says he agrees on the rules we created but continues to break the rules. I don’t really see what boundary I can set as he doesn’t really care to upset me – he probably gets fueled by upsetting me.

As it’s always about the kids well-being, I feel vulnerable.

It’s situations like past weekend.
– kids weekend with dad
– son has important test week at school and needs to study
– dad decides on a family weekend away. Son can’t join.
– I need these weekends to recharge as kids are 80 percent of the time with me
– son has no place to stay so I tell him he can stay with me
– daughter turns out to have a bad cold with light fever night before family trip starts.
– one of our rules is to inform each other about these situations right away. He didn’t until Sunday night after 10 pm when I was already asleep
– despite cold and light fever all weekend plans continue as planned (3 days full of activities)
– Monday morning daughter has a fever
– Monday is the day she will return to me.
– I have a therapeutic session planned for childhood trauma release but feel so frustrated and out of power that my mind is consumed with this weekend stuff
– I go ahead with my session, but pick daughter up right after and don’t have space in mind to sit with what I intended to sit with: healing some of my traumas.

I see that I frustrate myself. But I just don’t see how to feel in my power in a situation like this.

I feel so powerless.

Could you please offer insights for me to move forward?

Thanks so much!