ALL of that sounds retrievable, because my husband does this kind of mess regularly, and I always manage to clean it. For the baked-on stuff in the oven, you need to break out the toxic cleaning agents, though, which I hate to do, and it can leave scratch marks. The fridge seams can be cleaned with patience and ingenuity.
You are not cut out to be a landlord, OP, if you think that sort of mess is not salvageable. Also, you have no idea what actual damage some renters can do if you think this is bad!