Wayne,
Thank you for the genuine questions my brother!
I know you've read me stating that God is the Author of ALL things, right? Just like the author of a book, God has the details of every single thing down in His plan. This includes how I would influence the world in my little bubble, or you in yours.
I believe that predestination is just a term to describe God's plan. Often it is associated with salvation, but I believe it extends further into all aspects of the world. It is the acts, events, situations, etc. that God designed to reach a specific outcome the world is heading towards. There is not one thing that is excluded; for example nature, the devil and especially mankind.
The work I did before my eyes were opened was predestined by God. It was those works, events, situations and my choices that brought me to the point where I came to know God. None of it came about by chance, though before understanding the truth I believed in luck, chance and coincidences. Each event happened as He had planned, and continue to do so.
I might need some clarification on this question. If you do not mean that they are lost again, salvation withdrawn, I can address the question. None that are His will become lost again, returning to their former self.
If you mean those that stumble, fall, and temporarily depart from the faith; I would say that this time period is for a specific purpose of unique growth, and entirely part of God's plan. I know you've read
@Marvin Knox and his testimony regarding this exact thing. This time in his life put him exactly where God needed him to be, where he could be refined by the fire and come out of it better through God's grace.
Lord willing, neither of us will have to go through such a trying time as Marvin did.