Battle of the Arar 58 BC

[Bil_H]

I recently posted about the battle of the Arar on my blog but not surprisingly there are some outstanding questions regarding this battle.  If anybody here can help me pin down some of this information I would appreciate it.

1. Who commanded the Roman Legions that day?  Caesar states that it was himself, Plutarch and Appian both give the nod to Labienus.  
   
2. Which Legions actually participated in this battle?  Caesar makes no mention of the specific legions, only mentions three were present.  Some modern writers state that it was Legions VII, VIII, and VIIII, with Legio X sitting in the defenses blocking movement over the Rhone, which to be honest I doubt would still be manned at this point.
   
3. Where were the other Gallic tribes that set out with the four Helvettii sub-tribes during this battle?  Caesar only mentions that three of the four sub-tribes had gotten across, but makes no mention of the Rauraci, Tulingi, Latobriges, or the Boii.
   
4. Any realistic estimates of the numbers of Helvettii that took part in the migration?  How many were Tigurini?
   

Any help or links where I can find any of this information (if it exists) would be appreciated.