I've heard 300BB being a good approximate number for a limit bankroll, but assume less is needed in split pot games. The one thing I wanted to mention though is that formal bankroll requirements normally assume no moving down. You pick a bankroll so that the probability of busting is very low given your skill edge. But you can always give a higher limit a shot with a bankroll that isn't quite enough, with the plan of grinding back up at lower stakes if you lose a certain amount. Get some good experience and always the possibility you run well at first.
Nice work getting up to 40/80 FLO8 and good luck in your live games!