The jamming is possible, but highly unlikely. At 50,000ft, the energy levels required are just too high to effectively and reliably jam data links and GPS - especially when you don’t know where the victim of your jamming is located.
The antennas are shielded by the body of the aircraft. Then again, it IS theoretically possible.
Depends on what it's made of. Fiberglass composite is invisible to RF. Carbon and aluminum aren't.