Hi Eugen, [img]graemlins/happywave.gif[/img]
1. Number of charges depends on the wand. I've never used up all the charges in a wand, but I know that selling and buying back recharges it, as ZFR said.
2. Serak nailed this answer, too. I usually try to have each melee type character carry one "damage" weapon with a high speed factor, like a flail, axe or greatsword, and one "disrupter" weapon like a shortsword, club, dagger, even a longsword. I will sometimes switch if fighting a spellcaster. Weapon speed is also a factor I look at when deciding what magical weapons to keep and what to sell. And no, you cannot get extra attacks in a round for weapons with lower speed factors. I don't think the round ends any sooner. Pity.
3.
This site has specific info on creature resistances. Off the top of my head, I know that yeti take extra fire damage, and the salamanders take extra damage from their opposite element.
4. As ister said, non-detection only protects against spells that detect, like detect invisibility and invisibility purge. I've never found a use for this spell, and generally sell it as soon as I find it. However, it may have a use in one area that has monsters that can see through invisibility and stealthed thieves. I haven't tested it yet, but it's a possibility. To my knowledge, non-detection has no effect on the likelihood of losing your stealth while walking around.
5. Star-forged, hands down. I only use Conlan's against golems, unless I'm early in the game and have no better hammers. The star-forged hammer is significantly better against normal enemies. Hits easier and harder, and also gives some resistances.