Same departure, different return, different PNR?

Awards are always return tickets. You can't book a one-way, but you can have an "open-jaw" with a different return on the same return-ticket-PNR if it's nearer the departure than the target: eg OPO-VIE-BHX is OK because OPO-BHX is shorter than both OPO-VIE and VIE-BHX.

Similarly you can have an open-jaw returning to the same place from a different airport eg LAX-ORD // JFK-LAX, provided ORD to JFK is shorter than LAX-ORD and JFK-LAX.

The fee, unfortunately, is linked to the account not the flier.