I'm not an expert, but I think I can answer some of these.
1) If you take care of them, your hands shouldn't get really rough at all. I used to use a lot of hand lotion. As for dexterity, I don't see that you'd lose any.
2) Learning congas is fairly simple compared to kit. I don't think it would take long at all to be proficient if you already know kit.
3+4) I can't answer these at all. :\
5) Standing up with congas on a stand is not much different from paying it between your knees. A little adjusting for placement, but otherwise no problems. Standing with a sling isn't very difficult either, but you have to keep it still.
6)
Here's one and
here's another.
Like I said, I'm not an expert, so I wouldn't rely solely on what I say.
Mel