when u said gas in oil is that an oder or very strong smell ? because carb running engine dump more gas than needed and makes its way past the rings that dont burn in the cylinder. A brandy new crate motor will do this. u will always smell gas in the oil. And when u crank the motor by hand with a breaker bar and u hit the compression stroke it is extra hard to turn. do u hear any metal or knocking when u do this by hand at the point it stops at. i would check the battery by taking it out and getting and another one out of your suv and see what it does. did u find any metal shaving or chunks in oil when u drained it? 9 times out of 10 something will be in your oil when it lets go.