It's gotta be the starter. Dont' scrap it until you know what's wrong. Go to a wrecking yard and grab one for a few bucks, or look for a camaro on craigslist that is being parted out.

 

drain a little of the oil from your engine into a cup and see if it has water/ radiator fluid in it... make sure you do this after the car has been sitting for like half an hour or more. if you see or feel water (or anything other than what oil should feel like) your intake gaskets are leaking. water (radiator fluid) sinks in oil. if that is the case, you might as well replace the motor. this is what happened to mine. a hint would be white smoke coming out of the exhaust.. but its not always obvious. also, check your coolant level. you said you had an overheating problem before, this could be the reason for that as well. the engine is trying to burn the coolant.

the reason my car wouldnt start every time was because the water got in the cylinders and would not allow the cylinder to move. when i jumped the starter, water pumped out of the exhaust. btw my car had 159xxx miles on it.hopethis helps. sorry if thats the case.