Hey M,
first off i'd just like to say, i've been reading several of your posts, and i like your ideas, you seem well informed and have a knowledgable and creative way of interpretting the art of pick up that I am certainly fond of.
In respect to the few scenarios you specified, well, i'll go one by one telling you point of view.
Guy and female friend with no romantic potential is a subjective situation - it can depend on how close the two are? I mean, you could potentially cut this meeting up in to several categories, such as a collegue or simply a female friend. In any sense, if the girl has any manners about her, she won't let you pay for the whole meal, and atleast would suggest she paid half. This is how I would normally see the situation - So in that case, split the cost, or if you go out frequently and she may pay the next time?
Actually, instead of going through all of them, the simple answer in my mind is splitting, especially with the multiple group!..You're essentially right in saying that girls use the 'free ride'...but in general etiquette, I think we, unfortunately, get stung with the bill.
I doubt this was helpful at all

but i hope you could claw something away from it!
libertine.