Re: SpEn: Pick up confusion (it's easier to confuse things like death yaks than knock 'em out, and hibernation's blocked by rCold -- it also renders undead stabable!), and invisibility for a panic button/pre-major-battle buff. Mephitic cloud is still a prime target for spell acquisition; you occasionally manage to stab (It's a second tier stab, iirc) confused critters. Hibernation, confusion, and the cloud will more or less get you through a chunkload of the dungeon; my SpEn of Nemelex has cleared down to D:20, the hive, and all of the lair using those three almost exclusively... though nemelex summon spam kinda' wrecked some stuff I shouldn't have been killing at that point (Golden dragon, death yak herds, etc.).
Still, those three are your primary weapons until you can pick up something with more punch. Just don't forget to turn
off enchantments (Mine's been off since turn 2, currently level 15, at character level 17), and everything else except spellcasting, to maximize the XP spellcasting's getting. Also turn off small blades (Again, off since ~turn 2, currently level 12
), and stabbing after about 8 or 10 or so. Keep your defensive options (Stealth, dodging, shields -- get a buckler, if you can -- and armor, if by some miracle you gather up enough XP to use it -- troll/dragon armors can help there.) on, fighting, spellcasting, maybe a few more incidentals (Nemelex sprig's got evocation open, traps and doors, and conjuration until it hits 5), but spell schools and weapons need to be off.
Get some fighting levels in when you get a chance. Confusing instead of hibernating can stretch out a fight or five when you've got spare XP without putting you in much danger. 17th level SpEn's got it up to 7, which isn't bad.