pi4t: Ok, I'll offer some hints as to where you can find the others. Feel free to read or not read them as you wish, though it seems like you've missed a fair amount of things if you've only found three of them, so you might like to explore a little more too. Though I'll try to be fairly unspoilerish, and still have you use your brain to work out where things are, spoilers may appear, especially for anyone reading this who's earlier in the story. You mention that you're about to have the final boss fight? I assume, then, that you met Koveras a chapter or so ago? If not, then you aren't actually on the final fight yet, and shouldn't read on until you actually reach that point due to spoilers.

Dexterity: This can be found in a container of a guild whos members would gain greatly from its powers.
Intelligence: Also to be found in the city, search the shelves of a learned, though unpleasant, gentleman who asked you to do a quest for him.
Strength and one of the Wisdoms: Well, really, you return to your home at last and are eager to leave so soon? Especially when you've just discovered new secrets about it...
The other Wisdom: Wander around in NE Baldur's Gate until you encounter Marek, then when you next go to central Baldur's Gate a quest chain will begin which will lead to the possibility of obtaining this tome, if you don't give it away. I'm being a little more spoilerish with this one as it's the one which you can permanently lose, and I also suspect that it's probably the one you've used.
Charisma: Minsc and Edwin will both lead you to the correct area for this treasure.

Random_Coffee: I actually tried beating the boss today after leveling up Xzar, and i managed to kill him this time. The game informed me that it was the final showdown, and that i had completed the game, but i did it just to see if i could do it now. I will load a save and find the remaining tomes, so i can use them and have excellent stats when i import the character into BG2.

Thanks a lot for the tips :)

pi4t: If you've got BGT installed (or whatever it's called for the enhanced editions: it's the mod that combines BG1 and 2 into one game), then you can use the tomes on yourself and/or a number of other characters, and the increase will be brought into BG2. If you have it installed, then if you tell me what your party is then I can tell you if any of them will be brought into BG2 with their stats at their BG1-end levels. If you don't have BGT installed, then you'll probably want to use all the tomes on yourself from a metagaming standpoint, or at least those ones which will be somewhat useful to you (there's not much point improving your strength as a mage, for instance, so you may as well use that on a tank for an easier BG1).

Random_Coffee: My party is currently too weak to win the last bossbattle of Baldur's Gate 1. Three of them are level 7 and the remaining three are level 6. I need an excellent place for harvesting tons of xp so i can level them up a bit. Problem is, i have discovered every place on the map, and done all the quests i have gotten from random people in the wilderness. Despite this, i think that i have barely scratched the surface of this epic game.

So where can i find a place to get lots of xp? Haven't been able to do everything in Durlag's Tower yet though, but that is too difficult for now.

I am using the Enhanced Edition.