ترجمة - برتغاليّ -انجليزي - Ainda que as águas rujam e se pertubem,ainda que...

Speaking about God in this way, it should be the Lord almighty.

Yep!

Since I believe an authentic translation in form of book would available and considering that I don't have access to those books, would it be ok to attempt to translate this myself? I especially refrain from such efforts when the text is religious but... <shrugs>

I would say go for it. If you don't have access to those books, the requester probably doesn't have access either and you are giving a good (if not authorised) translation.