I got similar errors, but they were refered to tech descriptions.
That "Prometheus R" worries me. I assume that you deleted a consistent part of the ship's tbl entry...all specs regarding meneuver capabilities and stuff. Maybe you have replaced a line about subsystems with one about the loadout.
Check that suspicious entry and verify if I'm right.
Adding new ships to the list is easy: you have just to copy and paste their tbl entry where appropriate, paying attention on eventual mistakes. The ships tbl, however, has a certain ship limit. But you shouldn't have problems if you add five ships, for example.