Nice job. "Now I am merely skimming the music as a reminder of where it is going, but the actual music is playing in my head."
That's how it's done! The progress you've made in learning this piece will carry over to whatever future project you undertake. Even in sight-reading, the music in your head precedes the actual playing by a few mili-seconds, as you get more experienced in reading music.
It may take awhile, but one marker of progress is to look at a new piece of music, and hear it in your mind's ear, the same way we read words silently on a page. A worthy goal!
Tom