Need advice for husband caring for grandmother. His mom says he isn't doing enough but won't move his grandma into assisted living.

My husbands 89 year old grandmother has dementia and lives alone. His mom and aunt both live out of state so we are the only family in town. His mom is retired, but only comes up to stay with his grandma for a week every other month, sometimes only one week every 3 or 4 month if it's winter. This has left my husband as the only one here to check in on his grandma and care for her. Over a year ago, I emailed his mom to explain the depression, anxiety and stress she was putting on her son making him feel alone in caring for his grandma and explained how she was making him feel like he wasn't there enough for his grandma when she would call and tell him all the things he didn't do right (forgetting to weed the garden, or not mow behind her garage). I asked her to find an assisted living facility because being the sole caretaker was too much on him while both of us were working full time and raising a family with 2 kids. If she couldn't then consider moving his grandma down to live with her. She said she would consider assisted living if I would tour different places and send her the information. She wouldn't consider letting his grandma live with her. I set up tours, and my husband and I found a facility that matched everything his mom wanted. I sent all the papers needed for her to fill out and after hounding her for months, she finally submitted them, and the facility accepted his grandma. She was set to move in a few months back, but then covid hit. With covid, the facility wasn't allowing new residents to move in.
Now with our state opening up more, they are allowing move ins, but his grandma told his mom she decided she doesn't want to move. So his mom is now saying she will find an in home care place where someone will stop over a few days a week. That isn't going to solve the issue that his grandma is not safe living alone. It won't help with her forgetting to take medications (she has to take some 3x/day), getting up/down stairs (bedroom is upstairs, kitchen/living area is down), making sure doors are locked and she is safe. Her living alone will still have my husband feeling anxiety when he stops by as one of his main fears is being the one to find her deceased since he is the only visitor. I offered to walk in first so he wouldn't be, but he wants to protect me and doesn't want that to fall on me either.
I am at a loss for what to do. My husband doesn't want to fight his mom, and since he lived with his grandma for parts of his childhood, he feels he owes it to his grandma to keep taking care of her. I want to support him, but at the same time I see how it's affecting his health. He just hit 5 months of being sober and I'm worried this is going to push him back to drinking as a way to deal with the stress. Besides this all going on, we are both job searching as we work for the same company that was just sold off and we were told our jobs would be gone by the end of the year once everything gets transferred over to the new company. We have 2 teenagers at home going through the normal teenager issues and I'm going back to college so most of my free time after work is spent on school work and classes leaving him to do more around our house as well.
Has anyone had to deal with a mother in law pressuring her son to do all work and care for his grandmother? What can I do without outright arguing with his mom and threatening to cut off all ties with her until she makes a decision to move his grandma to a place where she is safe? His grandma has already had 1 stroke and luckily we found her in time before it caused too much damage. His mom has POA, and won't give my husband any of the information he would need to get more help without her being the final decision maker.