I have an exh who is a complete twonk and he has behaved very badly towards me, and at times our dc. He has done similar thing with the school and I believe his motivation was to try and make it look as though I dont let him know what is going on, yes its embarassing but it is just possible he is interested.
I have no time for my ex at all and truely would not piss on him if he was on fire, I cant begin to tell you just how bad he has been to me, and we just can not talk, I really mean we just dont talk at all. everything in relation to the children is done via email, its not ideal but it gives you time to think about what you want to say and is actually quite impersonal, you dont forget what you want to say, you can save and go back to it later to see how it sounds and from experience quite handy to have a record of stuff that is said and arranged.
You can not force him to see you ds unfortunately, its very hard and I do speak from experience, exh has seen our 3 dc 6 times (she is 2 and half) and not for over a year now, that is hard and if you are like me it is incredibly upsetting because you love you dc so much. But as a lovely friend of mine said recently to me when I was upset at his rejection of her 'its you who gets upset she wont know any different, kids are very accepting of situations like this'. Im sure you give your ds loads of love and attention.
I think quite a number of men (NOT ALL) also have trouble seperating stuff, so for example they will see paying maintenace as giving money to us their ex's rather than supporting their children and the same applies with seeing their children,
As he does not have PR and you do soley you can call the shots more.