Dexterity isn't really necessary for melee fighters, sure it helps their armour class, but has no impact on their ability to wield melee weapons.
The problem with Baldur's Gate and SoA is that the Paladin's been somewhat nerfed. for example a paladin should radiate Protection form Evil 10' Radius constantly (PFE itself has been nerfed to make things worse). They should also be inherently immune from to all forms of disease, and when wielding a Holy Avenger (Carsomyr) they should also continually radiate Dispel Magic in a 10' radius, which of course can be a pain as well as a boon. They also would get a personal Warhorse, and a mighty steed it should be, but not practical in BG of course.
There are downsides which haven't been implemented of course. Such as only being able to own what they can carry (bags of holding shouldn't offset this), should only own one set of armour and should tythe 10% of all gold acquired.
A paladin is the hardest character class of all to role play, in fact I've only ever encountered one player who did it well, and he's a legend amongst the AD&D players who remember him.
BG does make it easy to compensate for not starting out with high Strength, Dexterity and constitution. Not only can you increase all of these in BG1 by 1 point, there are also items which allow you to overcome the problem.*
As to summoned or conjured animals, they are real animals. Incidentally the Clerical spell Animal Summoning, shouldn't work in the Underdark as the sort of animals the spell summons couldn't be in range of the spell, but some leeway has to be given otherwise creating the game would be nigh on impossible. So the last comment was just an observation, not intended for once as a criticism.
* This doesn't mean i don't abuse the far too abusable character generation system to get the best attributes I can of course' I am only human after all!