A Tanks major advantage is it's breakthrough, allowing it to attack while taking less damage, Armor is only for whether it's pierce-able and how much Hard or Soft Attack applies to it.
You'd want to maximize your Breakthrough while having enough Soft Attack to push away Infantry (and Hard Attack/ Piercing to hurt enemy Tank Divisions, however for Singleplayer that's not important; Also Tanks are NOT meant to fight other tanks, that should be on an "IF" Basis, even historically)
The Supply Use is really poor, meaning that rarely will this tank Division perform perfectly as it creates a Black Hole of Supply around it.

I'd also recommend using Medium Cannon 2's on your Mediums and just ditching SP Arty.

On Attack values: While generally higher is better, there is a point where it will not make any sense to have more. Whenever you are fighting your Division will face hurdles such as weather, Combat Width, Terrain and others. A 20% Debuff on a Division with 700 Attack is quite a lot, 20% on just 400 Attack is much more IC (Industrial Capacity) effective.

The Fire Tank Battalion I'd switch with Light Tanks, simply because it's cheaper.

​

TLDR: Supply is really bad, Division is IC ineffective. Get more Breakthrough and aim for more Org. Maybe make the tank quicker ~ On overrun Division can't stop you. >Medium Cannon II is your friend.