I am very sorry to hear that about Mom. Our prayers are with you and the family
A big "hats off" to you for helping care for her. I think that's an important thing. The only meaningful thing we leave behind when we go is our family. Mom has a great daughter and son-in-law willing to take on this task.
My wife's parents live with us. Both had strokes. Mom died here at home 2 years ago. Dad has maybe a couple of months. The best care your Mom-in-law will get is at home. Love, attention, family, grand kids, good food, TV, dogs, cats, everything that makes a home. You don't get that in a nursing home.
I am not going to blow sunshine at you. It's a hard thing to care for sick parents and it will get worse. Your wife will need a break from time to time. You will have to step in. It will get overwhelming at some point, for both of you. Talk to your pastor, family, friends, maybe someone at a hospice. Make sure Mom has all her financial matters straight. Visit an estate planning lawyer if you need to. Make all the plans.
Yours truly.