how much exercise does he get on a daily basis?
Nipping/biting can also be an 'attention' getter, Maybe go back to your Dogtra trainer and use it for the biting? I'm not real familiar on the uses of e collars so can't advise on that.
I would up his exercise, have a tug/toy handy and everytime he goes to nail/mouth you, shove a toy in his mouth
These dogs CAN be mouthy, but working on diverting his attention to something else can lessen it.
Hopefully others will chime in with suggestions