Hi,
When you say you find pinch harmonics difficult with the Warpig, what are you comparing it to? Are pinch harmonics easier with the neck pickup on the same guitar or easier with a different guitar?
As regards the potential ground hum issue: the only thing you can do there is check and recheck with a digital volt meter that everything is wired correctly. Be also aware that positions #1 (neck only) and #3 (middle only) will hum more because there is no humcancelling effect. If you got a strong hum in positions #2 (neck + middle) and #5 (bridge humbucker only) but almost no hum with a different guitar, then the problem is with the guitar wiring. If you got a strong hum with a different humbucker equipped guitar as well you need to check the rest of the signal chain (cable, effects, amp, house wiring).
Good luck
Stephan