Hi Zach! Thank you for being so diligent in your reading!
1) There is plenty of access to potable water in the main areas of camp. The inn, the Adventurer's Guild, and logistics all have easy access to it, and most of the outlying sleeping areas are serviced by either a full bathhouse or outdoor spigots. Many people still prefer to bring their own water, but honestly I've been drinking from the tap here for years and never had a problem with it.
2) They do not. The amount in the current character builder is the correct amount.
3) Bad. Get the deep woods bug spray. I've never walked into a building at this game that did not have at least one can they're willing to share if you need to re-apply and are nowhere near or have forgotten your can, though.
4) You are considered to have basic steel versions of anything you have on you, including armor.
4A - Yes, you can bring whatever you have and are considered to have a basic steel version of each armament you are carrying on you.
4B - No, you can have as many as you can physically strap to yourself.
4C - Arquebus refers to all gunpowder weapons. As a side note, they are 99% flintlock pistol style at this game. On occasion we have approved different physreps, but these are done on a case-by-case basis after seeing the physrep in person and discussing it with the player. If you do not have one for this coming game, I can loan you one. You'll have to pick up the caps somewhere else, though - I have no idea where mine got to

5) This one's a little tricky, so let's see if I can explain it without causing more confusion

The weapon physrep itself is not fixed as a specific type, but would instead count as two different items. In this case, I would recommend getting item cards for each grip type (even just basic steel, which normally does not require a card). You can use it either one-handed or two-handed, but keep in mind that if you want to "switch" to use the differing damage type or set of skills you need to go through the 5 second roleplay time as if you were drawing a second weapon. You can always put two hands on the grip of a one handed sword, but doing this on its own without two separate cards or going through the roleplay time confers no additional benefit.