Well, here's Genesis 3:15 from the Septuagint. Which pronoun do you mean? There's no "he" or "she" there, mm, at least in the Greek.
καὶ ἔχθραν θήσω ἀνὰ μέσον σου καὶ ἀνὰ μέσον τῆς γυναικὸς καὶ ἀνὰ μέσον τοῦ σπέρματός σου καὶ ἀνὰ μέσον τοῦ σπέρματος αὐτῆς αὐτός σου τηρήσει κεφαλήν καὶ σὺ τηρήσεις αὐτοῦ πτέρναν "
"Or perhaps 2 Corinthians 7:10 where the Catholic Bible mistranslates the word "metanoian" as *penance* instead of the correct *repentance*?"
If it says "penance", then you are correct. The translation is wrong. It means repentance, but in the sense of a fundamental change in the way one thinks from a bad way to a good way.
What do you consider *true faith* and how do you determine if you have it?"
Orthodox Christianity, of course. As for determining if I have it, well, for me it's sort of genetic. I guess I just "know" it. I can see it in others when they demonstrate an Orthodox phronema in the way the live their lives and an Orthodox praxis in the way they worship. There may be others. I don't know.
Thr (ROMAN) Catholic doesn't use the Septuagint when it is not favorable to their "special" interpretation.
Look at Douay Rheims. Mom is correct.