So, the "concubine" thing is one of those points that I've heard variations on, where I think the story was that he was told to go live with a family, and the woman acted largely in the capacity of a caretaker or housekeeper, etc. On one level it might be considered scandalous, and then on another I thought Fr. Martin had been dispensed from his vows, and somehow partly laicized. Not sure on that one, but to me that's less important than whether he's telling the truth about other matters. We can and probably should give him the benefit of the doubt on that matter, since it really does not have any direct effect on us.
This is one of those things where Mr. Giuffre makes an interpretation of the situation, and those are the types of judgments that can be sorted out from within his story. So if he relates facts, like after Fr. Martin called me and said this, a week later someone was dead. But could it have been concidence? What was Fr. Martin's tone? Since we weren't there, he may have detected some tone that we might not have read into it had we heard the same words.
We probably won't know the truth in this life.