1) Well, a city with a thousand Drow could be made into several sections(Like Athkatla or Baldurs Gate from BG1), and it would be a good reason to actually sneak and be sneaky instead of just hacking and slashing your way through all of the Drow(Hey! Thats just how I sometimes do it, it's the easiest way),
2) The dragons are far too easy anyway, my Sorceror chopped up the black one alone, Minsc handled the red one alone, I never even had ANY trouble with the shadow one, Jan killed that one.
3) Well, a Stone Golem deals 3d
3-24) damage, has a Thac0 of 7 and 60 HP/ 14 hit dice, if that isn't trouble I don't know what trouble is,
Iron Golems have a Thac0 of 3(They easily hit you), 18 hit dice/80 HP(They can take a lot of shots unless the players have Monty Haul style equipment) and deal 4d10 damage(4-40!).
The only reason magic is so good against them is that Sorcerors have so many spells, and that the party is so big(I hardly ever have more than 3 PC's and 1 NPC in more adventures) that you have a wall of warriors and thieves protecting them while they cast their spells.
4) See 1)
5) ?