A relative was taking care of our cactus as we didnt have a certain home when we were

traveling. A year and a half later, skipping the details of our life... this is our cactus after getting returning. It is DEAD winter, Negative 50 with the windchill today, we dont have a great permanent spot for what i think this cactus needs, near all of the windows (where the best sunlight would be) is freezing. The picture is of its position to a window for the last year and a half and i have yet to move it or do anything until I get advice. It is doingn horrible, theres hair/dust/ whatever covering it, the soil is horrendous..

I reallllly want to save this guy! When we left it was dropping babies like crazy, hardy,fat, and completely upright. What steps would you take here?! Any help is much appreciated!!!