Make sure you have ship mesh highlight filter off. Also turn off skyboxes as they add more reflection on the ships.

Edit - It seems the highlight filter only applies if shadows are off...

Maybe you can look at fx files for shadows.

Increasing it makes ships appear brighter when you zoom in. Otherwise they look pretty dark.

Depends on your ships DA texture luminosity (Green channel) map and how bright you want them to be. Basically those lines in the entity file seem to be a lazy way to globally change the luminosity of an entity without having to change the texture every time (I used to do it the hard way until I figured it out, the results were basically identical to a global brightness increase on the luminosity map).

I usually use something like 0.1-0.15, though it's not uncommon for me to use <0.1 at times. Unfortunately this is not a setting that tends itself well to uniformity, because as GoaFan mentioned, it's heavily dependent on a ship's DA texture.

correct. Those are only used with the highlight filter. The light channel in the da texture can be used to illuminate an entire ship but I keep it all black too except for areas I want lit up. 

The setting in the entity is a lot better if you do need to add some extra brightness to the ship.
The 2 different settings;

minShadow 0.200000
maxShadow 1.800000

allows for zoomed out, which is close to switching to icon, to be set brighter where it actually needs it, zoomed in rarely needs the extra light.