Maybe try to view him as your child's father and not as your ex [if that is the case and may possibly be throwing a wrench in the machine?], whenever possible?

It may help to reframe your interactions and view of him.

If that particular change of perception doesn't help, maybe some other one will.
Finding a different way to view him and how he relates to you and your child and also to view his actions might help you to react to them better- you don't have to agree with everything, but it may make communication easier if things are less stressful on you.