Update I have ripped the fridge from the wall and found... a growth plus some dead roaches 
Ok had to crowbar the little barnacle off the wall but it came off after a few good hits. The fridge however put up a much bigger fight to be put back in place. After a whole 20 minutes of sliding and slaming it is now back where it belongs (with any luck permanently this time). Hopefully this helps any one with the same problem.
if you stand still, hold sprint, grab the heavy object, and then push/pull you are much stronger (not side to side, in my experience, and it can be a bit finnicky for some reason)
alternatively, I find crouching and walking into something, or pulling and jumping can make it much easier to move extremely heavy stuff
Nope, no luck, it seems like the fridge might be stuck on whatever that barnacle thing is on the wall. Any other tips? The fridge is practically unusable at this point because the doors won't close and it launches anything I try to place inside onto the floor.
Edit: I figured it out! I had a eureka moment and tried to use the broom to shove the fridge out of the way, and it worked! Turns out not only was it the barnacle/mold thing, but also like a billion cockroach corpses. I managed to push a space wide enough for me to crawl into, cleaned it up, then used the broom to slide the fridge back into place, and now the fridge is completely functional again. If anyone else has this problem, try using the broom from the supply closet!