DPBO: Is anybody having some difficulty with the swing meter?
Most of the players on here will attest to various swing meter issues. You're not alone on that one. (YankeeJim has some great tips for helping to fix them though)
DPBO: Is there a way to gage how much you'll lose when you apply backspin?
Absolutely. Experience. Yardage loss can change considerably depending on what club you're using, what ball you're using, elevation change, wind speed and direction, etc. Probably your best bet is simply good old trial and error....and take lots of notes.