Very nice to hear that you care about your MIL and what she's gone through in life. Seems to be such a rare thing nowadays with elders. So, kudos to you and your family!

It is also great to hear that your MIL doesn't have to worry about her children's financial well-being. That's a big relief.

One of the biggest challenges that your MIL is facing is depression. Encouraging her to go in for at least medical treatment, maybe even counseling, would have a great impact on her well-being. I am sure of that.

Have you considered the possibility of seeing if your MIL may be interested in moving? I only ask because it doesn't sound as though she's real connected with the home. She may see it more as her late-husband's, and not feel a warm connection to it. Whereas the basement holds a place in her heart. It's possible that it would be a relief for your MIL to have an entire house, that holds momento's and isn't a health risk.

That's my input. I wish your family the best & hope that you're able to bring some happiness back into your MIL's life. She does deserve it!