Right, his behaviour is out of order but my god, have you screwed up his financial stability and ruined any trust he had in you.
Why in the name of god did you ever ask him to take this loan out for you? He should have completely refused but he was young and obviously trusted his parents to keep their side of the bargain. But immediately you weren't able to do that and he's now paying back the loan, and having that loan is no doubt affecting his ability to get a mortgage. You say he was due to buy a house next year. What he buying a house with his girlfriend and she is now delayed getting on the housing ladder as well now?
I have sympathy that you have become ill and are now in a financial predicament but this should really not be your son's problem.
And bringing up what you've paid for private education? Surely you as his parent decided he was going to go to private school? How can you now expect him to pay for something he didn't ask for and didn't know he was going to be liable for?
And what was the agreement about paying the car loan? Surely if you agreed to pay this for him, you can't now go back and expect his to pay you retrospectively. Are you going to charge him for the nappies and formula he used as a baby too? His childcare costs???
And the PPs saying he should be paying rent... you agreed that he wouldn't to make up for him taking this loan out for you. Fair agreement imo. You can't start charging him rent now... just another agreement you'll be backtracking on.
Youve royally screwed up and I can see why he feels betrayed.
You need to sort this out and make sure he is not making these payments anymore. Sell the house, find some sort of paid work you can do from home. There are plenty of WFH/side hustle options if you just look.
But I fear that this will have forever damaged your relationship with your son. It very sad.