DY: Keys have represented the cross in Christianity for well over a millennium. There is a strong correlation between a key and a cross.
HaLeiVi: No, because “sanctifying” a Minhag from Avodah Zarah is an Issur D’Oraisa, no matter how the reason changed. Mattan Torah was able to change such things according to the Rambam. Nothing else.
LF: If you had a Minhag that was clearly Over an Issur D’Oraisa, would you keep it? Or would you realize that maybe a little Amaratzus creeped in over the Galus and that the Minhag was started improperly?