Oro left because it was discovered what he was doing. The manga even shows that.
And age in a manga can be a hard thing to judge.
Most characters look rather young unless they are as old as Sandaime.
Kakashi for example could look the same way he did when he was 30, when he will be 40 or even 45.
The timeline problem alone, if there is one, makes a weak argument for a completely new theory.
Because I gave you simple explanations for every other point.
I'm not saying you can't be right. To be fair, I don't know the databooks. Maybe there has been a clear track of the timeline that I don't know of.
And it's not that I don't like your theory. It's just that I think we need a little bit more facts to create such a theory than just the timeline problem.
It seems to be the only thing that could speak against my "one seal" theory by the looks of it.
"For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in beauty, in understanding, in skill, in strength and subtlety alike, of all the Children of Illuvatar, and a bright flame was in him"