1) Can I attach the Obi110 to my household phone wiring (and thus gateway all the house phones thru to Obi110).
Yes, just make sure no other services or equipment other than your telephones are connected to your household phone wiring before connecting the OBi110 to it or damage could occur.
2) Can I port my current Verizon cell number to Google Voice? (The number was originally ported from FairPoint to Verizon.)
You should be able to, but Google Voice does occasionally have restrictions. Only Google Voice could tell you for sure.