Do you guys ever know anyone got greedcard eventually still without waiver?
For your case, I don't think you have any opportunity to get a waiver based on "no objection" because that need at least one year valid J1 status, which you don't have. Probably you can seek to get a waiver without agreement from Chinese government.
For re-entry visa issue, I think it will be extremely risk because you cannot show your waiver approval letter. I suggest you think about visiting China after you get waiver. Good luck.