In Baldur's Gate 1 I'm playing a neutral good thief halfling, with proficiency in small weapons and slings.

I seem to be neglecting my stealth ability, instead using him as a ranged attacker, which I suspect is not the best course of action given that I'm only specialized in slings.

General battles are very challenging, mostly because of a high damage output, and it's hard to keep someone alive if the enemy is focusing specifically on one of my party characters. Any random ambush is pretty much a losing battle.

Anyways my general frontline characters are minsc and khalid, despite his personality he's the one holding the battle, more so than minsc, maybe I'm using minsc wrong, he's also dangerous to my own party if I berserk him.

I guess I have some thief fighting questions and some handling questions related to party members.

when hiding in shadows, the manual says the next attack will be a backstab, but also says that initiating an attack causes you to leave stealth O_o

Can a backstab be achieved with a ranged weapon?

How can I effectively use minsc?

I'm guessing I'm perhaps progressing beyond my level, and ending up with the odds stacking against me. I'm still level 1 and am trying to do minsc's quest, regarding the gnoll thing.

If you attack an opponent from behind with a melee weapon usable by single-class thieves while you are invisible and you have a backstab multiplier and the opponent isn't immune to backstabs, the attack will be a backstab. You become visible right after you've attacked. If you are stealthed you leave stealth mode when you initiate the attack, but it takes just under 6 seconds for you to become visible (assuming you don't do something that blows your invisibility before then). Give him a good bow, a two-handed weapon and keep him out of melee until he's got around 20-30 HP. The gnoll stronghold is doable at level 1, though there can be some encounters on the way (ogres, etc) that you may wish to steer clear of. It can be tricky if you don't have the right spells, however.

So that's what it means when it says it's leaving stealth mode, I was wondering why my character was stealthed even though it was saying I was leaving. Now it makes perfect sense, so if I hit the target within 6 seconds of initiating an attack I should get the bonus. I think I'm gonna wait a bit, at least until I've suited up minsc appropriately.

Gnoll Stronghold is a lot easier if you equip all your party members with ranged weapons, even without them having adequate proficiency.

Don't wait too long, otherwise Minsc might get angry that you aren't doing his quest and attack you.

The best way to use Minsc is to equip him with the bracers of dexterity, found on a troll(?) at the gnoll stronghold. You should always use him as your frontman, unless you have somebody with more HP. He has a high attacks per round with a two handed sword, and a good strategy is to have dynaheir cast web, equip him with Spider's Bane (a sword found in cloakwood), and berserk him.
As for backstabbing... equipment is your friend. Honestly, there is so much equipment that boosts hide in shadows that getting it around 50 will allow you to have 100. Make sure you grab the shadow armor from beregost once you can afford it, and there is a quest a dwarf gives you to recover his boots. Don't bring them back, identify them and keep them. Once you have a decent skill, the best strategy is 'hit and fade'. Scout ahead with him, and once you see an enemy, backstab them, them quickly run away. (boots of speed help for this.) once your character is out of the enemy line of sight, hide in shadows again and repeat. Notice how I said your characters, not your parties, line of sight, as they are different. Use coners to your advantage. The mage spell invisibility will work as well in an open field. Speaking of mages, you always want to backstab them first, not the fighters.
Well I hope that helped! As for experiance.... do a few quests in the areas west of the road to nashkel, they are easy to do and provide good XP. Have fun playing one of the best games ever!