Money:
Yes, we all have our own wallet (unless for some reason you don't want your character to, be it because they just steal stuff or the fact that they're so recognized they get items for free).
Yes, you're allowed to pool your resources together.
And no, there won't be an official "cap", but nobody is allowed to carry a million Rupees around with them. I'd say the technical "Max" for an individual would be 500-1000 like the largest.
Magic:
Magical Items can be used at will, but make it believable. Meaning, don't instantly pick up the Fire Rod and start making Flame-Torpedos that explode into mini Nukes. It's like anything: the more times you use it, the better you'll become with it.
I'm iffy about a lot of puzzles given the fact that stuff like that can take a lot of time out of the plot and usually kills an RP (for example: hunting for clues in a Scooby-Doo RP takes up 90% of the story, whereas 10% is actually catching the criminal and advancing the plot to a point where everyone wants to be). There might be a good dose of puzzles, but I'll have to give it more thought.
There won't be an official "system", but again, time and use gives you abilities. Plus, before each dungeon we'll meet someone who can grant us a new ability/item that we need in order to concur the evils within (I'll post something like "Darunia gives Mercanor the Bomb Bag and some Bombs. Darunia gives Deku-Demano a set of Explosive Arrows" for all the characters).