1. The
FAQ has a bit on this, but it's a bit hinky because it seems to apply in a very limited fashion:
Q: The Packmasters' special rule Running with the Pack and the special rule Beast Pack seem to contradict each other. How do they work?
A: The Packmaster and Master Moulder models are ignored when working out the unit's rank bonus, so only ranks of Rat Ogres count. Use the Packmasters' or Master Moulders' Ld value (or the General's) as the base Ld for the unit, to which you then add the Rat Ogres' rank bonus.
That, to me, sounds like you completely ignore the presence of pack masters and master moulders when determining ranks for rank bonuses. As Rat Ogres are Mounstrous Infantry, they would only need to be 3 wide to form a rank.
2. A
BSB is a character, and thus MUST be in the first rank EXCEPT where command would push him to back ranks. Now, as Rat Ogres don't have musicians or standard bearers that gets a bit tricky. Master Bred Rat Ogres and Master Moulders are both considered unit Champions (and thus command) and therefore have to be in the front rank. Theoretically, if you made your frontage small enough you could force the
BSB into the second rank behind a Master Moulder. (The
BSB covers models in a unit with different sized bases.)
Either way, I'm not sure the
BSB in your Rat Ogre unit is a very good idea. Firstly you'd need at least 5 packmasters for him to get a Look out Sir! roll, and even then he'd be less protected than if he were in clan rats or something. In a unit of Infantry he'd be unable to be hit by normal
BS shooting like bows. Thanks to the mixed unit rule, he could get unluckily plinked by a short bow or something.