Being a believer in getting it working right first, lets start with #2. My first bet would be a grounding issue at ether the input jacks or the volume pots. Looking at the layout for a 5F6A on schematic heaven, I am reminded why I hold the grounding of old fenders in such contempt. Try using clip leads from signal ground to the jack you plug in to and see it that kills the cross talk. If not move the lead to the volume pots and the lug that is grounded.