| 1. In theory you could roll 6 stats with each 18, a total of 108. But that's impossible. The best human fighter roll I've ever heard of was 99, but you could roll for weeks without ever getting it.
For a fighter>mage 93 can be considered perfect (3 wis, 18 everywhere else), but even getting this requires a lot of patience and luck.
Just roll as long as you want and take the best roll you got until then (use the store option).
Even a character with the minimum roll (75) can beat the game without too much trouble if you can't stand rolling.
2. str: to hit/damage bonus (melee or thrown)
18/01-50: +1/+3
18/51-75: +2/+3
18/76-90: +2/+4
18/91-99: +2/+5
18/00 : +3/+6
3. very long, might even be more than 100 hours unmodded depending on your playing style.
4.BG1 has an XP cap of 89,000 (161,000 if you have TotSC installed), BG2 2,950,000 (8,000,000 with ToB installed). Look at the XP tables in the manual to determine character levels at those points. Some mods change this. | 
Linear Mode
