Hi not an expert here, but I saw your question and got curious. I think you are better off plugging in just a RCA Bluetooth adapter, the USB port according to the manual is an A/D, D/A with 16 bit 44.1 kHz or 48 kHz, which means you will need some kind of interface, aka. a computer, to transform this into a Bluetooth signal with whatever codec. A Raspberry pi could do the trick but you have to decide if you want a plug n' play solution or if you want to experiment.

I don't think so. It sounds like you are trying to connect two input devices. The USB on the AT is supposed to be for interfacing with PC software to record LPs.

Unlikely on the USB-B, that would need a PC and drivers to negotiate and understand that it's presenting as an audio device. However with its RC out and adapters, you can get bluetooth transmitter/receiver units?