I would leave out the phrase "As I have told you in previous e mails" it sounds a little too terse.
I would also maybe ask him what he is proposing in terms of support and maybe trying to make it some sort of a compromise type situation.
Also, how old is D? Can she possibly be old enough to maybe be in charge of her own homeowrk when she is with her dad thereby relieving you of the pressure of having to be the bad guy? I know this is hard as I am always the homeowrk enforcer, my kids don't even bother to take theirs with when they go to see their dad.
