Hull point revision needed
Base Hull points as they are now:
Starbase 3000
Orbital structures ~ 4000-6000
Capital Ship ~ 3000
Starbases are much larger than anything else. I would suggest raising Starbase starting hull points to 9000 but making the defensive upgrade increments much smaller, focusing on Armor and Hull/Shield regeneration rates instead of adding thousands of Hull points. And of course the build time for a Starbase needs to be much much longer. Starbases could even start without Shields or Weapons to keep the initial cost reasonable. It should be possible to upgrade it with trading facilities before turning it into fully armed battlestation if that's what you need.
A fragile looking Frigate factory having more Hull than a Kol Battleship seems wrong as well but I suppose the structures need it because of the lack of shield mitigation.