1. Dex/Pie are the main attributes that affect your damage, as far as secondary stats, any physical stats work, i just started archer so i don't know if they like crit or atk power builds. you'll need a certain level of accuracy though.

2. yes their's essentially 3 tiers (cloth, leather, metal armors). I'm pretty sure Archers want leather and aren't capable of wearing the metal armors (again, just started archer, just kind of working off logic of what i've seen getting THM to 50).

3. an entire stack (999 arrows)

4. level 10

5. I'd guess Leathworking for armor or carpentry for weapons. however as someone knew to FFXIV, you should probably know that professions are like a whole new class. This isn't like WoW or Rift or GW2 where you can maintain professions as a little thought of byproduct and keep it up with the needs of your main class. If you want to level DoL/H you have to focus on it like an actual class. If you've got the patience it won't matter, if you're like me, you'll end up hitting 50 on your archer with your highest gather/crafting classes around 20.