1. That is oyur stadard tyre size right? I would imagine you could get anything from a 6.5 - 8.5" rim with that. Obviously 6.5 will balloon the tyre, 7.5 will be squarer, 8.5 will have an amount of stretch. Depends on the wheel design and how low you want to go.
2. Offset. Google the 1010 wheel calculator. I think the standard offset would be high 40s/50, sop if you kept the same offset but went with a wider wheel you should sit closer to flush. Or same width with lower offset etc...Depends what the wheel spec comes in really.
3. 5x112. Anything from Audi and Mercedes will bolt straight on.