How do I care for moy mother-in-law with dementia without any help from the rest of the family?

I left my full time job as a over the road truck driver and came home to help my in laws bc my 56 yr old mother in law fell up sick and ended up on dialysis with kidney failure, diabetes, depression, high blood pressure, COPD, and now possible lupus, along with that she has dementia/memory loss. She is mean, rude, calls me every name under the sun and I am barely getting any help from my father in law/the family. My husband & I gave up everything and moved in with them for me to help out. I feel like everyone is running over me, doesn't appreciate or even understands what I am dealing with. They all say "that's just her, ignore it, she won't do anything, etc" and when I do ask for help they don't want to help me or its a a bad time for them to help out. They just assume that I should do everything and then it back fires on me because its not right or I should have done more. I feel like they think that I have all the time in the world and they don't realize how much above and beyond I have gone. I did almost walk away at one point and it got turned around on me that I was a control freak, but when you have someone that is threating to take all their meds at once, or says they don't want to live, calls the cops on you at every little thing, or attemps to damage your property/steal your truck bc they are not getting their way. What am I suppose to do? How am I suppose to be able to handle that stress and feel like I can still have a life with my husband? I just feel like I have hit a point that I am not sure which way to go. Thank you