1) You can fit upto a max of 9J with the right offset, tyre choice and suspension geometry
2) The maximum recommended offset is ET45, although I'd imagine you could just exceed this (maybe ET42 with the right settings / tyres)
These parameters suggested above are dependent on whether you are running manufacturer specified ride heights or have slammed it on it's ****.
Whip rear screw out of rear arch liner if you are getting minimal rubbage
ALWAYS refer to a suspension specialist if you know you are likely to be pushing the limits
ALWAYS get a full geometry check if you are arsing about with settings (tyre footprint is the only thinkg between you, life and hedge)