Unfortunately the essay misses the critical scene where Frodo "untouchable now by pity" wields the ring and curses Gollum to "cast yourself into the Fire of Doom.'" But, yes even Frodo's fall was part of the plan.

I thought part of the point of men is that they are chaos agents. Elves and Maiar, tied to destiny, but men (and hobbits) have the freedom to choose for good or ill. I reckon Iluvatar is just justifying himself "Oh yeah, when Melkor did that horrible noise, I mean that. Honest"