I'm late to the thread, just popping in--I think you can call Adult Protective Services if you think your FIL isn't getting your MIL the care she needs.

There's something to be said as well for antianxiety medications, antidepressants, even antipsychotics--my dad was on all of these along with his Aricept or the newer AD med. They made his life much more enjoyable for him. He wasn't freaking out all the time and feeling suspicious like he had w/o the meds. Caregiving for someone w/ AD is very draining (I'm sure I'm singing to the choir here), and if she and your FIL already don't have a good relationship, this not-ideal relationship and caregiving frustration can combine and come out in unhealthy ways.

Dad lived on his own for a long time--every time we hired a support person he turned around and threw them out (or never let them in the door). "Luckily" he had a bad fall that required hospitalization. After that we moved him across country to be near my sister.

I don't envy you, caregiving from afar. BTDT.