It will work in both AMS and CDG when showing your Medallion status even with an non-status FB number attached to the PNR. Outstations/3rd party lounges: hit or miss. Works in BER ( 3rd party lounge ) but YMMY.
If you book using your statusless FB number you would be forced to pay for luggage and seats at time of booking. You might get around the luggage problem at the airport check-in showing your DL status but the better seats will be gone by then. But then i depends on your flying habbit, FB gold can be reached fast when travelling international C.