If you leave him to sleep normally, how long does your DS like to sleep?
If there are repercussions, ie melt downs, then it clearly sounds like 9 is too late for lights out.
My DS is lateish to bed, late riser, he goes up at about 7.30 usually, 7 if I can get away with it, stories and milk together and lights out at 8, and he'll usually drop off in 30 mins. I know that is even too late for him, and am slowly bringing it forward.
OK, so your self esteem needs a boot up the arse. If you are the one dealing with the fallout, then YOU are the one that has the last say. You have to set the routine if you can see it's negatively affecting your DS and all the more if you are the one who takes the brunt of it.
Ideally kids this age need as close to 12 hours as poss, give or take an hour either side.
School is so tiring, my DS is nearly 5 and in Reception, he ends up howling tired at the end of the week, hence the need for me to bring it forward.
I HATE dads that have FA to do with the end result, but have the cheek to lay down the law.
Parenting is a responsibility, first to the child, then to the parents, with the emphasis on the parent that has the bulk of the child care.
Can you not reach a compromise with him, because of the schooling, the melt downs H doesn't see, and because 9 IS too late in the week. Could you not say 7.30 lights out for 8 on a school night and later Friday and Saturday.
If you can't reach a compromise, then tbh, on your watch you need to set the norm. DS will get used to it, and once in a while, providing you make an adjustment the rest of the week, you ought to get away with it.
I found treating sleep like a bank balance, ie, a late night is a withdrawal, and needs to be made up, ideally in instalments. I'd make sure that if he had a late night, then I'd have to be a bit more regimented and not do too much with him for the next few days to allow him to catch up.
So get the DS sleep thing sorted, cos it needs doing, and then we can work on the rest of your issues!
If H is on the wane, then all the more reason for you to stand up for yourself. One, you have nothing to lose, and 2 if you do split, you'll be doing this on your own, so need to set YOUR routine.
You have more power than you think. Use it!
Sorry, that was long... 