Get moving you bunch of monkeys automatically ends the Command Squads activation once it makes a successful roll.
You roll saves against hits not damage. So one hit would get one save no matter how much damage it does. Damage Resilience will allow you to roll saves for each damage applied to a unit.
Support Weapons have one point on their damage track for each Soldier on the base. So if one soldier was already killed you would roll one less die for a template weapon. Keep in mind also that a Support weapon requires two soldiers to fire the weapon and other soldiers on the base can fire their other weapons. So a four man Support Weapon could fire its main weapon and two of their other guns. Once a man dies, they can fire the Support weapon and one other gun, etc.
This ^^ is correct.
Also, when a Unit Activates you have to declare all its Actions before performing any of them. For example, a Mechanic can perform 2x Makeshift Repair, but you have to say so before rolling any dice (i.e. you cannot roll the first 5 dice and see how it goes, and then decide what to do next).