Pudding that was great self control not to bite back in response to his email. You wouldn't be telling him anything he doesn't know. Your response avoids a text war, and keeps you firmly on the moral high ground.
Teabay that's an outrageous claim re the child benefit. You are the resident parent, and no doubt bear the majority of the costs towards your dc. I'm sure the added benefit of being in receipt of CB is that it entitles you to National Insurance contributions as well, very important as regards the state pension. Given the part time/lower earnings faced by many mothers, and hence far less opportunity to build a pension, this has always been an important factor.
Raspberry My ex and I share the weekend. He has Friday evening (generally no sleepover). I have Saturday, he has Sunday with (just started) a sleepover. But if one of us needs the whole weekend, or to swap the day, it generally works out.
It seems unfair on you that he has your ds most days from 5.30 to 7.30. This suggests he gets the "best" bits, whereas you get pick up, homework? bath and bed? What about having friends over for tea, or going to clubs. He may be too young for this now but it will happen. He won't want to go to his dads every night.
I presume he lives nearby. If so, could he do school pick up once or twice a week, and drop him back to you for 5.30? At least you then get one or two unbroken evenings a week.