Well the way I see it, if someone has gone to the trouble of building 3 full systems, and multiple windows installs to try and fix an issue, trying a wired KB and Mouse shouldn't be a massive hardship in comparison.
It doesn't mean you have to commit to using those devices moving forwards, it's just a troubleshooting step.
As for other ideas, have you used completely different disk drives and cables each time? Dropping from 140fps to 6fps is the sort of thing I'd expect to see when you have an I/O error or something (can be caused by dodgy cables even if using SSDs).