Sorry to read this Oscargarth - went through a similar thing with my DS and his Dad.
With homework, I resorted to not sending any with him to be done on the weekend, it was just pointless. Can you get it done before he goes? Sleeping in the same bed really isn't acceptable. My DS only had to put up with one woman allegedly visiting her father so she wasn't there on arrival on Fri eve, but by Sunday morning DS went into his Dad's bedroom - to find a new woman in bed with his Dad.
Your ex is never going to change I'm afraid, he sounds disinterested in DS (except for the control element I suspect) and is probably trying to control the GPs and family too, hence no responses to texts.
I did the same as you, through gritted teeth and encouraging noises, sent an unwilling DS to his Dads faithfully every other weekend. DS is now 12, his father has now emigrated (yes you guessed it to be with yet another new woman) and DS can see his father for what he is. So we've been saved, but I was getting to the stage of it being DS's decision whether to go to his Dads or not. It would be a not.
Until that time comes, all you can do is maintain the stability for DS at home, manage the fall outs and know that in a few years your son will see his father for what he is too. FWIW, my DS has nothing at all to do with his father now through choice - I set up a family counselling session for DS to tell his Dad about how he felt about the emigration, but mostly DS wanted to tell him that his new relationship abroad wouldn't last like all the others.
Be open with school if you need to be, get their backing and use that to perhaps get the contact order changed? Is that feasible?
Sounds like your ex isn't going to change things on the basis of his behaviours. Do you have a child appropriate de-brief when he returns from these weekends? I found this gave DS time to get it all out, give him lots of reassurance and hugs and settled him back into being home quicker.
Really empathise and hope you can make progress for all your sakes. x