[Bozos of Bones]

Two purposes: Aegis Of Rime, Aqua Mortis, Scion Of Storms and Soul Of Fire. These give 5 permanent resistance and 20% damage increase in Acid, Water(Ice), Electrical and Fire respectively. You need 4th spellcasting level and spellcraft of 10. Knowledge is used only to identify items without spells, Alchemy for identifying potions, and Spellcraft to identify what spells are being cast by enemy casters(the second use for it). 14 INT is enough to be full of class skills. Charisma 20 is a must for a 12th level sorcerer, and it really doesn't matter what you do with the other points. If you are planning to use a crossbow and not get into physical combat, you should choose dexterity over constitution. Strenght is also quite unneeded in thet role. Wisdom is usefull for will saves, and that's it's only use in a sorcerer. I'll leave it up to you to determine the correct ratio of ability points.