1) 1 SP (Starship) = 5 SP (Armor). See the
Conversion section.
2) Correct, a starship weapon does 5x damage to armor.
3) According to the current rules:
Rd - Th = Hd
Where:
Rd is the raw damage output of an enemy weapon, and
Th is the shield threshold
Hd is the damage that reaches the hull
Example: SDR 4 cannon is fired at a ship with 20 Structural Points, 20 Shield Points, and a shield threshold of 2. The ship takes 2 damage points to the shield and 2 damage points to the ship itself.
If a power armor with an ADR 5 weapon fires on a starship, it would do 1 point of shield damage.
4) Typically, a weapon's output, regardless of listed rate of fire, is based on its DR per combat round. Multiple weapon systems firing at once stack.
If you have suggestions for improving or clarifying the system/article, I'd be happy to hear them. I want to make it user friendly.