Is this unreasonable?

Fiancé and I have been dating LD for 3 years. We have a great relationship. Communicate well. Have each others back. Put each other first, etc. Due to certain circumstances, his mom has been living with him for the past couple of years. She is fully capable of living on her own. I am currently living here as well, but will be going back home for a couple months, then returning to live here FT. Without going into a long drawn out story, basically his mom treats us both as her personal maid, is incredibly passive aggressive, lazy, slams doors when she is angry, thrives on drama, lies about the smallest or biggest things, plays the victim anytime we try to have a sit down and communicate with her about anything, and treats not only us, but his kids like crap. We are currently trying to help her with section 8 and/or senior assistance living but she kindly told us to F off and she will deal with it herself. I told my fiancé when I return FT that I cannot continue to live like this and want to have my own place in his town until this situation can change. While he 💯 has my back when it comes to the way his mom is and wanting to fix this situation, he doesn’t want me to live anywhere but with him. I really don’t either but my anxiety is at all time high and I don’t know how much more of this I can take. Has anyone else been in this situation? How did you cope? If you read this far thank you!! I’m at my wits end.

EDIT: Thank you to everyone who took the time to read my post and comment on it. I read each comment and took them to heart and am thankful for each one. And thank you to everyone that continues to comment and post.