Fireship: not sure. Google translates "fireship" to "incendio" but then translates "incendio" back from Spanish into "fire". It doesn't translate "brulote" at all, but does give a definition in Spanish:
Embarcación vieja, cargada con materias inflamables y explosivos, que se utilizaba para incendiar grandes barcos enemigos abordándolos por sorpresa.
If I then copy that definition, Google translates it into a reasonable definition of a fireship.
Line 7 of "Sir Hew Dalrymple_dialog.h" ends with "Impressive stuff, Mr. ". "Mr." would probably better translate as "Sr." or "Señor". Alternatively, leave it untranslated, or expand it to "Mister". In English files, when a Spanish character is addressing someone, he is likely to say "Señor". In fact, there's a function in "PROGRAM\Dialog_func.c" which can generate a suitable title based on the nationality of the speaker and the gender of the person being addressed, so a Spanish character will always address a man as "Señor", a French character will say "Monsieur", and so on. So, even in Spanish, Sir Hew Dalrymple should say "Mr." or "Mister".
In any case, it must end with a title like that, not simply with "sir", because "Sir Hew Dalrymple_dialog.c" adds the character's surname onto the end. In English, then, what you'll see is "Impressive stuff, Mr. Hornblower." In Spanish, it should not end with "Awesome, sir Hornblower." Hornblower has not been knighted!
Historically, the word "battleship" might not have been used during any period covered by the game. However, there are several ships in the game which are called "battleship". (I tried looking at "RESOURCE\INI\TEXTS\SPANISH\common.ini" to see how they have been translated into Spanish. They haven't. That part of the file is still in English!)
Which of the storyline dialog files uses the word "battleship"?