great questions Peter, its obvious youve given this a great deal of thought, which is the first step taken already (a few people try to skip this step)

The best advise I can give you is to look at what the other good rambots have, and decide on which one would suit you best. For your first robot at least, copy something that works.

examples.

pillow torque - astroflight 940 with 15:1 gearboxes and vantec control. brilliant but expensive.

stiff breeze - 12v gold motors, over volted with 2 stage 10:1 (could be wrong ratio) and sidewinder control. good balance of power to cost.

one of tonys dragons - ev warrior drive, with gearboxes, not sure of ratio, sidewinder control. massive power, but heavy solution.

or drop me an email, as I sell complete drive solution, speed controllers, etc etc

good luck, and id speak to the rambot builders about you questions on shock mounting etc, as they would know better than anyone. contact me anytime if you want info on which bits to buy.