1. Yes, you get a talent point every odd level IIRC. Some of the requirements are going to be adjusted / removed.
2. The traits are are an either/or bonus, they don't stack. I think currently if you tie they cancel out (when they should stick with the previous bonus).
3. Have the person who learned bartering talk to the merchants and do the trading. If you loot everything (sneak before trying to steal around town), you should eventually have more gold than you know what to do with.
4. Yes, I believe there are still improvement to be made for dialogue in co-op.
5. Only if you are caught in the act. A lower reputation will increase prices at merchants, and eventually cause NPCs to either refuse to speak with you (may be able to bribe them into liking you more) or automatically attacking you on sight.
6. When attacking there should be a backstab icon if you are in the right position.
