Making Starzard part 2

While making Starzard I encountered a few things

1.  Ranged weapons are a big part of Starzard. I'm wondering if I should make ranged attacks an opposed roll or an unopposed roll.
2. When making a melee attack, I wanted the player to make only 1 defence roll (ranged attack, if you roll equal or higher, you deflect or successfully dodge the monster ranged attack) or 1 melee attack against a monster with multiple attacks (i.e monster with 3 attacks rolls 3 times, If any of the rolls is higher than the player, it will deal damage. On the other hand, if the player's roll is higher than any of the monster attack rolls, he will deal damage). 
3. Should I even implement usage die mechanic using d6?
4. Vehicle and Starship stats is almost similar to Robot Commando (a sci fi Fighting Fantasy gamebook) and Stellar Adventure (a sci fi version of AFF). The combat is almost similar to personal combat of Spellzard. 

What do you think?