Re: How do I turn off power from PK3
There is a note under Project properties> Conf>PICkit 3>Option Categories>Power:
Selects the target Vdd voltage level that PICkit 3 will provide. This setting will NOT take affect immediately after being applied. Instead it will occur the next time MPLAB communications with the tool (e.g. by programming/reading/running etc.).
As I understand, either you unplug then plug the PICkit programmer, or restart MPLABx to make your setting effective.