Hi I am a student from China on F1 visa, and I am doing an OPT now. I used Turbo tax for 1040EZ and found out that I can get a $280 refund. When I used 1040NR ez (on my own, so I might have made mistakes), I owe the government $980! That's a $1300 difference! I have $5000 treaty so in then end I might not owe as much as $980. But if I can, I'd rather file 1040EZ and not take advantage of the $5000 treaty. Can I do that?

Besides, when I did turbo tax, they said I can get a state tax return of $420. Am I eligible for that at al?

On F-1, every one is exempt from residency for 5-years. You must file nonresident tax return Form 1040NR or 1040NR-EZ with form 8843.
Turbo Tax will not do this return. It must be paper return, can not be efiled.