I think you're reading Marius paying Thermadier to go away wrong. Thermadier was, and will always be, scum. From the battlefield looter to when he first shows up to him leaving for America. No money can change who he is.

Jean ValJean being given the candlesticks at just the right point and in the right way in his life to make a difference is really the only part of redemption in the book.

Javert committing suicide at the end was simply because he could no longer pretend that Jean ValJean was utterly an purely good. Which would make him the bad guy. It destroys his worldview so badly that the only way (at the moment) he can resolve it is to die.