Honestly, I don't get it. What is his plan with this?

He's trying to reverse time to the point before the FL plunged the sword into the mirror and cause the time loop, to do this he had to fully become one with the story but at the same time possess the skills he already has. That way when he reverses time he won't follow his timeline but the story's timeline.

Oh that makes so much sense! Thank you very much for the explanation

TY king