1. the two-year-service policy is an agreement between the Chinese and the US goverments. it is really not easy to get waiver as your supervisor told you.
2. you want your degree more than anything else, right? then you have to stay in China for a while. there is only one way that you might re-enter the US and that is you will stay in the same program and apply J1 visa. the problem is how many chance that you can get it.
3. do not even think about other visa type. there is no way to get other type of visa before you get your waiver.