1) The draw result seems to be automatically ignored, so its technically a 50% chance of winning each hand. I assume this is to speed up the process.
2) The numbers definitely change, but the numbers are based on a weighted ratio between your Charisma and your target's Charisma. I tend to boost it pretty quickly, so I often see 3:5 or similar match-ups against a lot of the early-game characters (or my co-op partner, who doesn't invest in Charisma at all). Even the woman taking a bath (can't recall her name off-hand) granted me a straight-up 5:3, and as near as I can tell she's the most difficult person to "argue" with in the first map.
3) This seems to immediately prompt a straight-up percentile check based on your skill versus their skill, with no "intermediate" levels of success (ie, one bar fills up or the other one does, but neither will fill up partially - as it might do if the RPS games were still happening "behind the scenes"). If you have the advantage in an argument, it almost never pays to auto-resolve - because statistically, you actually have a better chance of success if you play it out. When you're at a disadvantage, auto-resolving is slightly safer.
4) That, I couldn't say. But honestly, I think it's really just a straight-up coin toss since it's (more or less) a 50% chance of success each time you click the button. It's really kind of a waste of time, much like the "social" mini-game from Oblivion, but at least it looks pretty. :P
