Most can carb and dispense 8 kegs (or more) off a 5lb fill. So 5 kegs and weighing the CO2 cylinder...I can believe you'd be just shy of 2.5lbs of liquid CO2 remaining.
Thanks for the feedback on this. The rule of thumb is you need 1/2LB of CO2 to push a 16gallon keg, so technically this should push about 24 of the 5 gallon kegs. This probably drops in half when you are force carbonating.
Thanks,
Todd