1. Either slavery like everyone else said or selling a large stack of a certain item you don't need to other players.
2. Faction is your own choice, as long as it's a player faction, you should stay away from NCR in general if you want to progress in-game.
3. Don't bother.
4. 30:13 has Khan raiders, those give FN FALs and grease guns... Seems newbies love those and that's apparently what you're looking for, otherwise Unity is the weakest thing that is truly worth farming.
5. All small guns are shit.
6. Nein.
7. Build tons of private bases so you can just add your alts to them without having to create dozens of tents.
8. Banks are useless.
9. Most people do it alone with a proper build afaik.
10. Most casual players and trolls do, you won't see many PVP apes or good PVE farmers staying in NCR for more than an hour or two.
11. CAMKII.
12. 150% is enough, 100 is not very effective.
13. No, the minimun accepted for a combat skill is usually 180%.
14. Special encs in 2238: bunker with gauss pistol, special vehicle, abandoned howizter and family grave.
Nothing in this game has a chance of 100%, you will always have at least 5% chances of failing miserably.