You do NOT need a US address for the FCC "licence". I got mine here in the UK last year and all for US$60.
As for flying G reg on an FAA licence at night - I think you will find that in euroland night flight is considered as flight in instrument conditions for which the JAA night rating covers. As the FAA IR is NOT valid on G reg, it does seem that it cannot be done. My feelings are to get it in writing from the CAA before night flight in a G reg.