Some comments based on things from your OP
For him it's about sex and what I can do for him financially or otherwise Yes I think you are right here.
he owes me a large sum of money and not once out of common decency or manners did he run it past me or check that financially I was ok over Christmas. What about checking you are ok or paying you back first out of "love."? What you are asking for (common decency about settling, prioritising or even acknowledging repaying a loan) - and not getting - is how normal people would treat a stranger.
He always, always takes it for granted that I am ok. Never occurred to him that it was what two people in an adult relationship do. That's because he doesn't love you and is not in an adult relationship with you, he is just using you for sex and money, as you have already noticed.
Completely fed up with being treated as an afterthought , his constant need to pacify his ex and his sense of entitlement. I don't blame you. He sounds awful.
I really don't feel that we are equal partners That's because you are not.
He thinks I am hung up on her No, he is. But you know that.
If I am honest I love him to bits Seriously? For the love of God, WHY? You are aware he is unkind, is using you for sex and money, is hung up on his ex wife, and that you are not an equal partner. Just why are you still there?