Who gets looked after

I can see that you really appreciate the loving qualities of the woman you have married, her sense of responsibility and care for someone who can no longer control how she behaves. I can also see that actually living with someone who mistreats your wife the way her mother does is is very painful for you, probably more so than for your wife who is probably used to it. Also she has to give more attention to her mother probably than she does to you. All this makes a relationship very difficult.

The hard thing to say is that this is your problem, you cannot solve it by moving other people around. There may come a time when your wife cannot cope with the physical demands of care and then it would be appropriate for her to move into a home. But I suspect that she would not be happy with herself if she put your needs ahead of her duty to her mother as she sees it.

You would be advised to talk this through, but my advice would be to get yourself a place of your own, so that you have a bolt-hole when things get too much for you. You could find your relationship improving if you see your partner less often and she can perhaps arrange some support so you can have proper time to enjoy each others company. Trying to displace her mother will I fear be an uphill task, that may well end in your splitting up.