You seem to have blown this out of all proportion.
He was letting his house to his sister and his ex. That's fine. It's his house, he can let it to whomever he wants - and as his ex had previously looked after it, she was probably the easiest tenant. You can have a purely professional relationship with your tenant.
When you visited, the house was not free. It was rented out. It was not his to put you in. It would be like if my landlord decided he wanted someone to stay here - he can't; legally this is my home until the end of the agreement.
Do you have an issue with him having exes at all? Would you rather he wasn't in contact with them? That isn't something you can enforce, but if it's going to cause big issues for you, you're better to end this now and look for someone else. You may have to accept that a lot of people in their 40s and 50s have baggage, though.
You've twisted it into some strange challenge, where he allocated empty houses to women and gave you the worst one. That isn't realistic.
I'm surprised he's stayed around for you to be so irrationally angry for so long, if I'm honest. Infact, the reasonable concern here would be whether he's put up with your complaints and arguments just so that he can come live with you in the UK, because you'd have exhausted most people's patience by now.
It's advisable to stop drinking if it's causing fights, too. That sounds like the start of problem drinking.