i ran 2 bottles (10lbs bottle) with the ZEX kit on my stock 94 CX . . . i used the 55 jet. . . will using nitrous you have to run colder spark plugs, and most importantly run rich. the nitrous makes power by adding oxygen to the combustion process. so as long as you have enough fuel, you won't lean out, melt pistons, and blow the big D16.
i can't really help you, but to have a fine tune of No2/fuel you must use an Air-Fuel ratio meter.
What do you mean saying "How big of a shot ...." ? => you want to know how long you can run No2, don't you? or maybe you want to have some info on jet sizing?
on stock internals you don't want to run any more than a 75 shot. But even then you run into problems in the long run. i would save your money and get a good set of forged pistons. this will help you out also look at high flow fuel injectors, fuel rail, fuel pump. and do a search for posts about nitrous.
for your app i would look at a zex kit or nx express. because of easy install i would go with zex but i would save your money and do a cheap tubro with stock interals because you don't have to fill a botle and other minor things.