Pedantic.

The campaign book states that stations are treated as ships for the purpose of resolving attack effects. Thus, if an armed station "activates" before Defiance, does defiance get that extra die? And does it work against the independent station?

Feel like I should also point out that against any station (armed, unarmed) Paragon would trigger, Sloane would trigger, etc... So the question here is does the station "activate," or does it just "attack" in place of a ship activation?

No, the station just attack instead of an activation (that's in the base defense objective, in Independen Station objective it's just an attack after the command phase)

Hard to say. We track activations on sliders and revealed command dials and the station has neither. I'd say yes for consistency, but no for the RRG.

As @Lemmiwinks86 said, you don't activate the station so no Defiance.