Some of you should lose your free bag, as you are no longer a card holder and so the MP (no longer OnePass) account waiver no longer applies.
However:
1. DOT rules require the same allowance on one itinerary, so since you have a free bag on the outbound, the same will apply inbound.
2. UA and Chase will not talk that quickly for UA to remove the Chase "note" from your MP number.
As for showing your card, even after it is cancelled - that is pretty unethical, honestly. It might work, but it's not right.