Although it may make some sense to consolidate all aircraft into one or two units, this may actually reduce their ability to function.

Fuel is really the key here. Aviation fuel is obviously only available in very small amounts, most of which is simply what's left over from the previous few years of operations (very little new stock coming into Europe after 1997-8).
Physically transfering the aircraft from one location/unit to another is going to take resources, namely fuel. This will either be aviation fuel burnt through flying the aircraft, or other fuels burnt by trucks.

Transporting any additional aviation fuel is also going to be costly, perhaps even more than shifting the aircraft themselves as it'd be a case of having to collect a few litres here, a dozen more there, etc.
Ammunition and spare parts (used or the increasingly rare new) are also going to take effort and resources to shift.

It might actually be more economical to simply leave the aircraft where they are and only consolidate when, or even if, missions allow.

There was never such a model of the Apache. It's always had the 30mm autocannon.

I am not sure it was a typo. I still think they took the total number of vehicles in a division and divided them by 6-13 (to match the tank ratio).
72 M109 -> 9
408 M2/M3 -> 43
232 Tanks -> 18
24 M691 -> 2
24 MLRS -> 4
132 Helicopters -> 4 (ok it breaks down here but not as much as you think if you double the 13)

If you apply the tank ratio to the M2/M3 you get 31 yet if you add the M920 and M18s assigned to a division (as they are also M2 chassis) and divide by the tank ratio (~13) you get 43. The fact that they say that a battalion had 70 IFVs make me think they did include at least the M920s.

I think their ratios were:
Rear area (ADA, artillery) 1:~6
Front line (M2/M1) 1:~13
Helicopters 1:33.