1. I gather it uses a points system . What is the points total of a standard game?
Depends on which expansion you use or which game you use. If you play 40k it'll prob be like that where the game varies on the players or the TO. Average seems to be 150-350 for tournaments in Dust Tactics no word on what it is for DW.
2. Is it possible to field an all mechanized force in DT/DW?
It is possible but you still need a minimum 16point Hero. (Saying 16 points bc both sides have their cheapest Hero at 16pts). This is also only in tournament rules. Friendly games you can have as many as you want. Some scenarios limit the number but you can also no go by the rules for the scenario and it shouldnt affect the game that much.
3. Does it have some sort of force org/required units in each force? Are certain units restricted in how many you can field?
Like I said b4 only requires 1 Hero in tournaments and can have up to 1 Command Squad per armor Value.
I really like the Axis walkers and wqs hoping to build a mechanized company/formation. Is this feasible?
Yea you can but again one hero required. My advise if you need that one hero use Rosie shes an anti tank person and she can repair a tank. Also you cannot make indirect shots with artillery if you do not have units with artillery strike. You could take Manfred, Sniper Squad or Spotter Squad, and a Command Squad. So you can repair tanks and call artillery and only have 3 No mech units that would be behind the line of tanks to suppose them. I would divide your tanks with anti troop and anti infantry if I was you.