1. “Does TRUTH always reveal itself DURING the lifetime of the person ruined by falsehood?”
I’d think not necessarily. This is an ‘alma deshikra’ – world of falsehood. Though, of course, Hashem is there behind the scenes taking note and running the show according to His script.
Eventually, the truth comes out. There is a medrash on a possuk (remember only very vaguely, have to find it) that says ‘can a person do [evil] deeds in private and I will not show him to others?’
2. “Can a person daven profusely for a yeshuah, and simply not merit it?”
There is no short, or clear answer to that. There are so many different variables. However, our job is to continue to daven. By davening we improve ourselves and become more meritorious and thus more likely to deserve the yeshuah.