Signs of dementia or mental health. Any ideas?

Hi, I’m new here. I’ve been on the web looking for answers and help especially!
My hubby is the only child to his parents dad 87 with Alzheimer’s and his mom 80, who we think she might have early dementia or mental illness. We lived 2 hours away, would drive down every week to check on them especially my FILaw, stay for days at a time but it was extremely hard cuz my 15yr son needed us too.
We would get horrible calls and messages from my MILaw to my hubby, he is a horrible, loser son, why don’t you help your mom, take your dad I can’t handle him, so on & so on!
It was so horrible at times we would just pack nd leave.
But we started noticing the verbal abuse towards my FILaw was extremely ugly & uncalled for. Example:
We had left their house one time, about 20 mins in driving back home we received a horrifying call from her that he had “fallen” in the shower and passed out! We called 911! Drove back and stayed few more days. Before discharged, I received a phone call from the charged nurse, that my FILaw had old and new bruises all over his body! That what’s going on at home, who’s living with him, so on & so on? I said, only MILaw! It dawned to me at that moment it’s her, my MILaw. He didn’t fall, he was beaten & hit on the head that caused him to fall & pass out! Hubby & I couldn’t believe it or pretty much couldn’t accept it. His own mum. So I told the nurse let me talk to my MILaw. Nurse said no I have to report it. I convinced the nurse not too that we will handle it! It was the worst mistake we’ve made! The guilt of now how bad things are. We sat in our beds nd cried, how could she be doing this?? How come she’s a different person around us? Why?
So that day we decided to sell or home and move in with them in there 4 bedroom home! She’s been asking us for yrs so we decided to make the big step.
OMG.. everything was about to change moving in! The neighbors told us about her screaming & name calling in Spanish, etc. why now are we being told about this? The neighbor would sometimes calm her. All this time, who are you? Her true colors we coming out by day 2 moving in. My poor helpless FILaw was being tortured, beat, mocked, verbally abused, punished “not being fed”, no grooming, etc. Why? Didn’t we see it? She manipulated us when we visit that everything ok! But the phone calls was proof enough. We just thought she needed caregiving help. One day, 5150 was called bc of a mental breakdown. She was admitted to phyc and they prescribed meds. First 2 days was a whole new person. Then, she told her sister about the incident. Her sister ordered her not to take anything bc nothing is wrong with you! MILaw stopped all meds nd accused us of drugging her nd thinking she’s crazy. My hubby family gets involved all the time nd we end up being the bad ones cuz of the lies my MILaw creates. Hubby talked to them asking them not to get involved bc whatever she says it’s lies and they don’t know what’s actually happening at home! Instead of telling her to stop they bad mouth about us, she believes it.
MILaw had one of her family friends report us to social services for a bad word I supposedly said, of course not true, bc I don’t speak Spanish.
Social services did a report, I proved to them she needs help and why aren’t they helping. I have so much proof of her actions and abuse “videos & messages pics etc) She started to believe me. And it was dropped of evidence. How ugly that we have to protect ourselves bc of her lies.
To make it short, there’s tons more horrible stories but now we afraid bc now she’s turning on the gas stove on blast everyday to hurt us. We’ve started noticing more of forgetting names, lost car keys when there hanged up in the same place, laundry washer full of our clothes when it’s hers, double dosing my FILaw with his meds, not paying bills on time, forgetting how to use her cell so she goes to T-Mobile everyday, repeating the same story in one day. We take the abuse ain’t leaving to protect him constant abuse