How does Combat Work with regard to Companies?

As best I can tell from my time last night, if a unit dies in combat it doesn't come back.  There appears to be a unit count on the portrit as well.  And I couldn't find a way to train a single unit and add it or the like.

One thing I would like to know is when a squad of units are fighting, does the attack just roll 1 number (max attack of all the group) or does it roll an attack for every person in that group against random people from the other group.  If it isn't rolling individual attack vs individual defence then that might explain why all the army techs are a little OP.

IF there is a way to add a single unit or make  a single units into a squad, I havent seen in.

The other thing is if you group units together but then split your party in the same tile, I have no idea how to make them group again.

I noticed an interesting bug with the individual units in a company dying off. Even though they die, the entire group's attack and defense doesn't go down. I believe the game normally divides up the attack and defense up amongst each of the figures in the unit. As far as I've been able to tell from testing, the game divides the total attack value between each figure in the unit, with each figure making a separate attack. The problem is that when figures are lost because of damage, the total hp, damage, and defense are still the same. It doesn't get reduced as figures are lost from the unit, so a unit that had 12 figures, with a total attack of 96 would then become a single unit with attack of 96 making it wayyyy too powerful.