Divorce won't help the situation as honestly I can't pay for the stuff with him in the same house it is not going to be sorted by divorcing.
When you say "it is not going to be sorted", you mean that divorcing won't keep you in your current lifestyle. No, it won't. But that is not the point of divorce.
So you want to maintain a certain lifestyle, with a big house and DC in private school, but you can only do this if DH is working.
But he is not working.
So you are considering selling a rental property, and your shares, and have already borrowed from his mother, to keep DC in private school and prop up this unsustainable standard of living.
What happens when the rental is sold and the shares sold, and you can't pay his DM back, and DH still hasn't got a job, or only has a low-paid job, and he still has other debts (the ones which he wanted to use the money from his DM to pay off) ?
At what point do you accept the inevitability of pulling DC out of private school?
Or, if it is your number one priority to keep them in their school, are you going to sell the home you live in and downsize (after selling everything else)?
So you will be heading into retirement with no assets, a smaller house, and a far more modest life.
The bottom line is that you can't force DH to step up and give you the lifestyle you want. Trying to force him is just making you angry.
It would be better for your own sanity and emotional wellbeing if you accept that he is just a dead weight who contributes nothing, and that it is solely down to you to provide whatever education and lifestyle you can afford for your DC.
When you reach this calm acceptance, you will be ready to divorce him.