My husband has a semi backbone when it comes to her. He doesn't like to hurt her feelings but I think if I was upset and needed boundaries enforcing he would step up to the mark
You need to be 100% sure of this before you go any further with this plan. You also need to agree who is going to be the carer for her. Many men think that you will do this because you Have a vagina , even though it’s his mother and not yours. So it’s possible you are both assuming that the other will do this.
You need to agree as many practical things as possible .
Sit down with him and a a piece of paper and write done how often he will visit her each week, what he’s prepared to do himself and what he will buy in help for . Cover everything you can think of - does she need help in the garden and a cleaner now? What about later if she needs help with cooking, shopping and personal care? What if she gets dementia ? What if she needs to go into a home?
Does your husband work and if so is he willing to give that up or go part time to be her carer ? If not, who is going to do this or pay for this ?
Will she come and live with you if necessary or will he go to stay with her for part of the week ? ( so she will need a spare bedroom ).
You absolutely MUST think of practical things like no stairs and accessibility to house and garden . Otherwise she may end up having to move again in a couple of years!
Does your husband have POA for her? Does she have a will?
Before you do anything else ,spend an entire evening reading the boards here on MN about caring for an elderly relative and write down all the scenarios you can think of and discuss them with your husband .
DO NOT DO THIS if he’s not willing to talk to you about this, if he says things like “ we will work that out at the time “ or “ I can’t predict the future so there’s no point in talking about this “.
What that means is “it will be your job to deal with it. I will be too busy at work / on the golf course “.
You don’t mention children but if you have them, think hard about the impact this may have on them.