弱虫な私にはサヨナラするから

It would translate something like "I'll say goodbye to my cowardly self, so" - the 'kara' has the nuance of "I'll do it". It's like telling someone - perhaps yourself - you're doing it. Imagine it like... "mou anata no koto wo wasurenai kara (, yurushite kure)" -> "I'll never forget about you again, so (forgive me)"

>>359 Perhaps it seems like strange Japanese because it's in a song and a song would utilize non-standard use of the language. or well, I'm assuming it's in a song, because it sounds like one. >>358, is it from a song?

This is my take on >>358, anyways. I have taken the liberty of making it a bit more lyrical (nanoha!), but as usual, I suck, so...

I have also changed the order of the sentences in the translation in some parts as it would sound strange in English otherwise. Stuff in [brackets] are the literal translation in case you're confused why what I've written seems somewhat different from the actual words.