You just need to give everyone a ranged weapon. Ranged combat in BG1 is godlike. Slow walking speed + low hit points + extra attacks per round = lots of dead enemies. When looking at spells, unless you are attacking really high level enemies, don't even bother with direct damage spells. Disablers like Horror are amazing.
Heck, when all else fails, you can always run away. There are very few things that actually run faster than you and once you get the Boots of Speed you can run one character into sight range of the enemies and then kite them around while the rest of your group fills them full of arrows.
Finally, wands. Wands of sleep, wands of paralyzation and wands of monster summoning. These are your friends. Sleep for the mooks, paralyzation for the big bads and monster summoning for your meat shields.
BG1 is tough, but it's not impossible. Unless you are playing a mage with 3 con on Insane. Then it actually is impossible. That 1 damage flame arrow at the start does two damage and a 3 con mage only has 2 HP.
I haven't played this in about 3 years. I actually played BG2 first, and when I finally played 1 it was so dang hard! But it has a certain appeal to it. Never got any further than entering Baldurs Gate though. One of the toughest enemies I ran into were those miserable succubuses.
As for boots of speed, I had to use gatekeeper... I think that's what it is called, it's been so long. Otherwise isn't there like only one or two pairs in the game?
Right now I'm playing NWN2. No eps for it yet. Heck this was just given to me a year ago. Only trouble is, I think I accidentally selected the wrong voice for my barbarian. Big brute of a guy with a sissy voice. I'm so disappointed in that. Almost makes me not want to play but it's too late to change it now.
Also I play Sims 2!! Yippeeee!!! I love it. I have every single ep for that. Maybe I'll share some screenshots with you all if any are interested.