Higher PF raises? Yes, until you find an amount that only 1 or 2 people will call
Less continuation bets? A little less, you have to hit something against calling stations
Limpng? With pocket pairs and big pairs in EP if there is alot of PF raising
Loosen up pf? No, usually too many players in the pot
Tighten up pf? Yep
More calling down with marginal hands? ie Top pair Only against loose aggressive/maniac players, never call passive players w/ one pair ever of course. Waiting for big hands and opening more tables and set mining or very TAG is easy on these types of tables.

Your win rate might just be a little bit of variance, although 5.5 BB/100 is pretty good still. I would figure you probably have enough of a bankroll (over $1500) to start playing the NL50 tables, considering your last 70K hands.