as far as how many CO2 cartridges, a 12gr cartridge can take my 700x32 tire up to around 80psi. plenty to roll on (max is 85psi) and i've got more if need be.

i don't carry a pressure gauge. "firm to the squeeze" sidewalls are enough for me until i get back to my garage.

i carry three cartridges with me. mainly in case of a dud cartridge (happens once in a great while) or a second flat.

if you get a flat on the morning commute and fill it with CO2, then work 8hrs, i'd check it before i headed home in case it needed a top off, but it should be fine. just make sure you bleed/fill it with a regular pump when you get home. it would lose about half the pressure in 24hrs.

there are a -ton- of "chamois creme" options out there. i use Bag Balm because i can always grab it at the local pharmacy or grocery store and it works fine.