1. Replace only the chaincase cover (kit), ...you may have to shave off the tabs depending on clearance from your "drop and roll" and your silencer.
2. The MViper kit I purchased came with a 39T gear, ...you should be able to get pretty close to your ratio by dropping the top 1T.
3. I'm guessing the MViper kit added around 5lbs., ...you could rig up a cable, ... but most of the weight is in the gears, ...I wouln't give up the durability and ergonomics for 1lb.