I know it sounds stupid...
But when you cut your GPU power almost in half... You turned settings down a lot right?
That would cause the crash, and sometimes a crash just kinda sticks, no fans, no lights, no output.
You have to flip the switch on the supply and do the hardest of reboots.
Like I said, you probably already did that stuff. But I've seen it happen.
The first thing you should always do is try turning it off and on again