The massive power increase from a small overclock and overvolt sounds like it is near thermal runaway. The hotter silicon is, the "better" it conducts electricity, which can cause excess power draw and various other potentially big issues if you go too far. I know the temp was about the same, but there is a breaking point when the voltage gets high enough at the same temp.

It would not surprise me if getting the temperatures down would also bring power draw down quite a bit in that case.