What is better for a paladin with maxed strength and 3 dexterity, dual weilding holy avenger and then eventually the light of cera sumat with the Golden heart of charname or single wielding the holy sword or golden heart?

Take into account that my paladin won't be able to take ambidexterity because of his low dex and he can only take two weapon fighting(as far as dual wielding feats go)and that shields are useless as i have way too little AC(because of dex again) for it to be of any use in HoF(which i am now in).

BTW i have an aasimar paladin and that the unused longsword/s will most probably go to my cleric/monk/paladin/rogue(does anyone know if you can finesse longswords cause i am fairly sure in NWN you couldnt,)

You can only Finesse light weapons and longsword isn't really that. The penalties for dual-wielding without required feats are so heavy and the benefits of dual-wielding are so low, that you're infinitely better off with a shield +3 or some such. Especially given your sucky DEX. BTW, you're getting an AC penalty for each two DEX points below 10. In your case, it's -3.

i know i get a a penalty to dex for every 2 points below 10 though i think it should be only up to the maximum bonus to dex allowed by the armor i'm wearing. Thats why i am going to get hit all the time no matter how good my shield with the only use of having one being the special abilities it may posses.

But i guess you are write about there being no point dual-wielding as i just noticed that the number of attack per round is capped at 5 and i can get that already single wieldin the golden heart.

BTW i actualy get a -4 to DEX