Jonesy89: intelligence also affects what level of spells you can learn (only a mage with 18 Intelligence can learn a level 9 spell, for instance).
True of normal dnd 2e, but by my understanding, that isn't implemented in the game.
Everything else you said, though, is true to the best of my knowledge and for the purposes of BG1. There are a few exceptions in BG2 (such as the spell 'wondrous recall', which lets you regain 2 lower level spells you've already cast), but they're not in a vanilla bg1 install.
I'd be interested to hear how you got the stats you did. Did you not reassign points after you rolled, or did you just not click reroll too often. While your stats are probably better than most NPCs', they're surprisingly low for a player made character. In particular, that 15 strength may hurt you on a fighter. In general, any stat within the range 8-15 is quite similar: other than carrying capacity and bashing open locks, you'd have had exactly the same bonus ((ie none) had you taken a strength 8 fighter! Not that I'd recommend that, either, as you can still increase your strength. If you make another warrior type character at some point, I'd highly recommend getting strength to 18, as that'll give you an exceptional strength bonus (the game will write your strength as 18/xx, where xx is a random number between 01 and (1)00. That'll give you a bonus over the standard 18 strength of between +1 damage and +3 thac0, +4 damage, depending on how good the xx is. What's more, if you get to 19 strength (there's one item in bg1 which can permanently increase someone's strength by 1), your modifier's will be above even the maximum 18 strength bonus. To clarify, this is part of a table I copied from the internet. The first column is your strength, the second your thac0 adjustment, and the third your damage bonus.
15 0 0
16 0 +1
17 +1 +1
18 +1 +2
18/01-50 +1 +3
18/51-75 +2 +3
18/76-90 +2 +4
18/91-99 +2 +5
18/00 +3 +6
19 +3 +7
The other stats don't have the 18/xx system, but it's still useful to get them as high above 15 as you can. Don't get me wrong, you should be able to adventure using that and high stats aren't a necessary requirement, but you might have made things harder for yourself.
Thac0 stands for 'to hit armour class 0', and is the number you have to equal(?) or exceed on a d20 (20 sided dice) to hit an enemy of AC 0. Lower is better. If the enemy has an AC of 1, then you have to equal or exceed 1 less than your thac0, while if their AC is -5 you have to equal or exceed 5 more than your thac0. It's a very awkward way of expressing a very simple system. Also, bare in mind that a roll of 1 is always a miss, and a roll of 20 is always a (critical) hit.
Oh, and while someone will no doubt disagree with me on this, I'd say it would be better to put points into just one missile weapon, and one melee weapon, on a fighter. You can only use one at a time, after all, and the more points you have in it the better you'll be attacking. I'd suggest going for large swords at this point, as several classes (eg thieves) can only use small swords in the bladed department, so you'll have to share the loot between you. They also deal less base damage.
Oh, and when choosing what to put points in in your party, try to spread what people use around. From experience, I can say that there are few things as frustrating as getting an amazing spear which no one can use, while you're hunting for yet more large swords.
Regarding your party comments, am I to take it that you have Imoen, Khalid, Jaheira, Xzar and Montaron as your party? Yeah, I think that Xzar/Monty and Khalid/Jaheira will be at each others' throats sooner or later. You've got some time, though: plenty to get to Nashkel, anyway, and you can get some NPCs better suited to you there. As others have suggested, I'd recommend Minsc, for humour and because he's a great NPC. The slight downside is you'll then be locked into choosing Dynaheir as your final NPC, and she's fine and a mage, which (if I've surmised correctly about your party) you don't currently have. You won't be able to pick her up immediately, though, as you need to go on a subquest to help Minsc get her back first, so feel free to pick up another NPC in the meantime. SPOILERS: At the carnival, there's a statue of a woman, with a person near it trying to sell you a hideously overpriced stone to flesh scroll. Don't buy from him, buy one from the Nashkel temple or (if you don't have the money and/or don't mind the slightly cheap 'reload until it works' strategy) pickpocket him with Imoen for it until you succeed and he doesn't attack you. Use the scroll on the statue and she'll turn out to be a quite powerful good aligned cleric.
There's also a mage you can get at the end of the Nashkel main quest activity, but I wouldn't recommend him for a first run. He takes quite a bit of effort to work correctly.
By the way, there's another benefit to using the Minsc/Dynaheir/Jaheira/Khalid/Imoen party: it's the 'canon' party, that is the party which the plot of BG2 involves the PC having completed BG1 with.