[AZKen]

Should not be any actual oil coming out of tail pipe. Probably condensation mixed with tail pipe carbon/soot. Don't worry about that. If there is no blue smoke at tail pipe or oil fill hole/breather hole, you don't have bypass. Conpression test will help with that theory.
Blowing out lines while connected is a NO!
You said you cleaned the tank and put in new sender with new sock? A pump flow test will tell you info. If you think lines are clogged, replace the rubber ones. Disconnect hard lines at both ends and blow out. DO NOT blow into the tank or pump or carb.

Yuo need more test miles before more remedy.