Your chip is bad, man, that DFI will unlock 100% stable.

I used that mobo to unlock a 720 and three deneb 5000+, all were very easy to do and all those chips were good. I was using the August 20 bios for all of that, and everything worked perfect and the chips would clock clear up until either their limit or the DFI's HT Ref limit with 100% stability.

I would try each ACC value between -12 and 12 on all the cores and see what happens. If that fails, try vcore, but it's likely that your chip is not a good unlocker.