This document
http://www.usfirst.org/uploadedFiles...r%20Curves.pdf gives you some rough information on the motors.
Free speed is the speed of the motor, with no load... you will never get quite that high as there is always drag on the motor, from the gearbox, if nothing else. For a simple, first order approximation, say the CIM is running at 4,000 rpm, divide by your gear ratio (typically about 12:1 in a toughbox) and then multiply by your wheel circumference to get an estimate of your robot's top speed.
I beleive if you search for "JVN's Mechanical Design Calculator", though, you'll find something even more useful.
As for the tube weight, I don't have access to a KoP, so I'll leave that to someone who does.
Jason