The hot spot

So when we moved into the house almost 2 years ago, I kept burning and overcooking food. It was really weird because I've never burned things before. A couple of months later, I was telling my neighbor about it and she said I should get an oven thermometer since the oven is so old. It's original to this 1979 house. So I got an oven thermometer and lo and behold, the temperature could be off anywhere from 50 to 150 degrees! And I have to try and turn pans around so things get cooked more evenly. The bottom of the oven is more hot, so when I put pans on the bottom rack, things...such as sugar cookies...tend to overcook. So now, I've learned to adjust the temperature and constantly keep an eye on the thermometer. Sometimes, I've checked on food that is supposed to be at 350 and the thermometer says 500! I hate this oven! I know the owner won't do anything about it till it just dies.