Obviously, somebody needs to get involved with this mess before your POS uncle ends up loosing everything, including your Grandma's place. You might want to see about having somebody who is trustworthy, get involved to the point that they have limited guardianship, and a clear path to protect her if she ends up with unexpected financial or health issues. Probably wouldn't hurt to have a local, highly regarded, lawyer step in and determine exactly how badly the uncle has damaged all parties involved, and what to expect as he slides down the rabbit hole into bankruptcy.
One point to consider here. There are often serious misconceptions about exactly what a teacher's pension is worth in our society. I'm not speaking for every state and situation, but some of the pension systems suck to the point that folks are pretty shocked when they hear the truth. Here in PA. there has been exactly one COLA in the last few decades, and the demented far right legislators take great pride in preventing any possibility of having others. This means that many very elderly retired teachers are now down to a few hundred a month in payments, which was a great help decades ago. Now, it pays the taxes and not much else. Bottom line is that you may be blown away to discover exactly how small your grandma's monthly income really is. Good luck.
BTW,Don't forget, there is one in every family. My mom died four years ago. Left a million dollar estate for me to distribute to three of us. I then discover that my little brother, 38YO, is destitute. Defaulting on his house, $140K in CC debt, no job etc. Had a six figure income selling software, lost it when the depression hit, kept living like the king of stupid, but switched to CCs to keep the game going. Four years and $325K later, still no job, no savings, no clue............