The 18 Str and 18 Con were planned, and probably essential. Elmonster's run started in BG1, went through BG2, and then finished TOB (including a tougher bosses mod). 18 Con + con tome means he only needs 1 more point of Con to regenerate without any other magic items. If you go through the journal, you see he does quite a lot of physical attacking in BG2 (especially after getting staff of invisibility (archmage)). There are, apparently, 3 tomes for Wisdom, and Identify can deal with a low Lore early. Later, he'd have more than enough Lore anyway. I can't speak for most of BG1, since the journal doesn't cover it.

As far as cheese goes, he used quite a lot of it to make it through the game, especially in TOB with the tougher bosses mod. Sleeping after most fights would be a minor thing by comparison.

When i play BG i always play as a wizzard. At the beginning he's rather weak, compare to other classes, but he trully shines later on. I must say, wizzar is op at the endgame so much, that it si almost cheating, broken character :) I mean Sequencer, and other simmiiar spells lets you get super defens in second, while you casting stop time, acceleretion, comet, Abi-Dalzim's Horrid Wilting, and immortal magic missles in baragge.

And if this won't help, there;s still Imprisonment :)

What, why? Mage, even if single class, wreaks havoc! Stop trying to solo in 1! It is next to impossible. If you don't you use scrolls of powerful spells, at least (that cost much money). Has very few spell slots, is terrible at melee, has abysmal HP pool.

Try killing Firebead Elvenhair a coupld of times, with export and import, to build a few easy levels! Also, recruitable NPCs will be met at higher level if you do this. Use scrolls and wands abundantly. Especially the stun wand is hot stuff. Change the group formation, and make certain your main mage stays safe behind! Also, don't forget to invisibility/greater invisibility your way, past threats that you can defeat by no means at all (much like the Iron Throne top floor on first visit there). Keep fighters in front row, thieves and clerics to the rear, and mages (you) at the tail, back.

You cannot mage solo 1, unless you are the definition of hardcore gamer. Or unless you use it in a multiplayer game and utilize the so commonly discussed, game exploits (NOT console cheats). But in 2, the mage is outstanding. You can even raise an army of planetars and like 12 duplicate clones of yourself, all at the same time!

Keep your mage, beat the game, enter 2, and keep it a generalist mage (or wild mage, if you want some satisfying risk factor). Robes of Vecna, amulet of power, Golem tome, circlet of the Netheril, improved cloak of protection +2, ring of acquity, ring of wizardry, boots of speed, belt of inertial barrier, and there it goes. Happily dangerous cheesehead trolling everything around.

Good bg1 spells are ‘sleep’ and ‘Invisibility’… the first one will knock out a mass of peons and the second one last a long time to allow safe travel on the dangerous roads.

You could also try bard for good all round character or just collect wands--- Mages become VERY powerful in the late game but that’s a long ways off.

Good BG spells:

Charm, from Algernon's Cloak, is the better one.

Magic Missile. Especially for interrupting enemy casters.

Chromatic Orb from high level mage. Ruins enemies, with stun.

Web. Perfect to stop a crowd of enemies and pin them down. If you wear the ring of free action, all the better for you.
Horror. Good one, but a gamble.

Knock. For all your open locks (chests of doors) needs.

Blur and Mirror Image. Individually good, but as a pair, is 1's ultimate magical defense combo.

Fireball and Skull Trap. Massive damage. Skull Trap works best either on unsuspecting enemies, or fire resistant ones.

Dispel. It's obvious. Undoes enemy magical protections. Your own too, if you are too close.

Haste. Turns fighters and front rowers into freaking ninjas.

Greater Malison. Makes a spell easier to affect an enemy. Lowers their chance to roll for foiling its special effect. Perfect before a chromatic orb, a hold person, and others with particularly nasty special effects.

Improved Invisibility. Much better than the simple one.

Fire Arrow/Melf's. Good for high level mage only, and strong enemies. Damage adds up over time, added with acid/fire one. Good on enemies with much HP.

Cloudkill. Fart it towards an army of enemies, especially right after one web, and/or stinking cloud, and there you go. Also, it kills the expansion's final boss in only 8 seconds.

Monster Summoning 3. You know you love it when the big bad ogres come to you as alies. Or something else that reminds undead, is not one, and has stun (?), sorry don't remember the name.

Hold Person. Keeps an enemy human, or humanoid monster, pinned down for enough time to kill it. Or escape it. Am not very sure, but i think it worked on some undeads as well.

Otiluke's Resilient Sphere. Keep a nasty enemy out of play for enough time, to kill its companions, and prepare better for facing it.

Sleep works wonders in BG1. Enemies rarely resist it, but is TOO cheap.