I'll give it a go as well:

1) No clue. The only thing I can tell you about Agility is that is seems to go up when I use a lot of physcial/weapon attacks in a battle.

2) Hmm. Well, some canes cast spells when used as items in battle, so if Maria is a Mage for you (most people - myself included) turn her into a Mage of some sort), you could give her a Cane for some extra spell-age, but I don't see why that would have to be her primary weapon or anything.

3) Yes. Fists + high Str = pwned. Seriously. High level Fists can deal some serious pain, especially if you go for 2-Fisted Action (i.e. no shield, unarmed for BOTH arms).

4) Every game has to have a total loser.

5) This is unproven, but in MY experience, the fewer attacks it takes to end a battle, the more Gil you get. Try fighting a group of wuss monsters, like Goblins or Hornets, and kill them one by one with physical attacks. You get, say, 6 Gil. If you fry them all at once with a single spell, you can get up to 60 (!) Gil. It's really weird.

6) I'd say no. Pick an archetype for each character and focus on their strengths. An entire Party of Red Mage wannabe's is bad, mm-kay?