1. I think all you need, Point Balnk Shot, Rapid, Many, Improved Rapid and One Shot.
2. Only the One which purchase for the Feats.
3. Go with your forging Toon to Reeshov Forger and see what you can forge.
4. See 2.
5. Few Guilds are active, for Arcane Society try to contact Guild Master at Forums, be nice, sweet and helpful maybe one day yu get an Invitation from O Guild, for other Guilds try to contact Guild Master.
6.Each kill is a Roll and all depends on Luck. CR of Enemies, your own Level compared to CR of Enemies, EX mode, all has an Impact for the Chance to get a Rare Item Drop like Crook or Set, for Crook think Enemies should have CR 28 ( but not sure ). Partysize increases Spawns in some Areas so higher Killrate and better Chance for Rare Drops too. So simple logic, when you Need half the time to clear an Area on EX4 compared to EX6, EX4 would be the better mode as Killrate is higher and each kill is a Roll.
7. See 6.
8. Main Idea for Rare Drops is, that they drop rare, play Long enough, than you really dont know what to do with all the Crooks.