Make all fighter turrets into guns. Freighters and SHF's retain their turrets. Allows you to balance freighters and SHF separately in far better detail.
Nerf 2.00's efficiency into the neutron star's gravity well. It's all about well timed and aimed salvos. I think your problem is that they just deal too much damage in short period of time. This would discourage it.
Buff 4.00's efficiency to make them more spammable as gun that does not really have its own niche.
Keep 8.33's as they are.
Edit: Furthermore, I believe 3.03's should be at bare minimum 700 m/s guns.