What do I do about this poor pitbull of my dad?

Im 19 and my dad's pitbull [i think he's mixed, but whatever] is about two. Every time I go to visit the dog, I pet him, and my hand is pure black from the dirt he wallows around in. I have a feeling it isnt dirt, because he's a junkyard dog around cars and such. Dirt isnt that black and dusty. It could be mixed with car exhaust or spilled oil. He's constantly scratching himself, and after 2 years, my dad finally took him to get neutered, but refused to pay 40 dollars or so for flea med the vet reccomended. He says all the vets want is money, and he can cure his own dog. The dog has an attitude problem, and he wont take the dog for training, either. Even if I offered to pay the 109 bucks for the course with my college loans! He feeds his dog alpo [the dog is very hefty] and even when I offer to buy better food, he refuses. I cant keep the dog for him. Im in a 1 bedroom apartment with my mom. His first dog was shot because he allegedly bit a robber/customer & never reported it. He got this one for replacement.