From my short experience as a modder, I've found two comfortable ways of including text on a mod:
1.Using localised strings directly with the tools you are using, this way is the easier one, but the mod creators usually only put the english string, leaving the other ones blank, so that's why you see no text in some mods. You are lucky by only lacking the text, it sometimes crashes or does unexpected behaviour. This usually makes translating harder, since you have to look all the text in each file through whatever tool you are using. You can look at the official documentation for localised strings here.
2.You can append text to the tlk easily by using TSLPatcher (not sure if it works on Xbox 360), where you can reference all the names and descriptions as StrRef(x), where 'x' is the position on the append.tlk file you created with any .tlk editor. I think this way is the best for making translations, because you can have things more organised . You can download the TSLPatcher with its documentation here (sorry, it's only in English, however, I can help you if you want, as I speak Spanish too).
The porting work you have done looks great, hope you keep doing that 😀. I don't know a lot of Kotor Xbox modding, so my information may be wrong.