My main problem with this spell is its potential for damage. 1d6/attack for the whole day is immense, along the lines of epic immense.
Limited to just one attack a round; this gives the 1st level mage (without using any of your extra damage ideas) the ability to do 14,400d6 damage/day with a 1st level spell, a 1 gp gem, and a potion of Cure Light Wounds. It never runs out of ammo; its always ready (cast it first thing after regaining spells), gives you the option to fire with both hands if you have two potions (and 2 gp to spare on gems).
It is not a touch spell, so the spell continues even if you cast another spell; there is no "holding the charge" thingy to worry about.
How many 1-5th level mages could afford to buy both a crossbow and 10,000 bolts? This spell puts the cost at 1 gp and a potion (potion not used up in the casting).
This spell is much too powerful for a 1st level spell:
Strong Points: duration, damage potential, low material component cost, strange focus component with possibly minimal cost (or no cost at all if the item is simply borrowed to cast the spell), range increment of 100 feet (is that considered thrown for up to 5 increments; or is it device propelled and 10 increments?), no save, no spell resistance, no damage type, useful with a plethora of ranged feats and several melee ones, uses Dexterity instead of Strength for attacks, uses 1/2 Intelligence mod for attacks and damage in addition to BAB, uses 1/2 wiz level for attacks and damage in addition to BAB, extra damage for focusing and building up, and no ammo limitation.
Drawbacks: attack roll to hit, moderate damage (for a missile weapon), material component required, focus component required.
This is just my opinion, but I would not allow this spell in any campaign I run without majorly toning it down. Why should anyone buy a bow/crossbow/ insert missile weapon here: take one level of wizard and choose this spell and you are set.
Ciao
Dave