Wires are Fun, Fun, Fun

My buddies 93 teggy ls was pulled over the other week for his third brake light being on, even when he's not touching the brakes. Officer told him he's need to fix it or he'll give him a ticket next time. For now he took out the bulb but it's a very strange problem. He bought the car last summer from a shaddy dealership and ever since then, it's done this. Also, his clock dims whenever he hits the brakes and his corner lights up front turn on when he brakes as well. Now the obvious starting point is the fuse box area but would could've caused this? Anyone ever had or heard this before? What should I really look at first? I'm sure someone can help!