Dear John:
If I understood your situation, you need to do some recitals. I think that's the perfect way to balance the progressive study and the "missing gaps", as you said. By the way, it's very important to do both, always: you can't quit learning "your-level-plus-one" pieces, but it's fundamental also learning easier stuff, specially those you never played (composers, styles, etc) and general basical repertory (such as the inventions).
As I said, plan some recitals, where you can play new things (both hard and easy), with mastered works. For instance, let's assume that you play a couple of Bach's WTC and a suite by him. That's about thirty minutes (or a bit more). With some inventions, and even some Anna Magdalena, or Little Preludes, you would have a nice, varied, interesting, all-Bach recital.
Another example: you play Beethoven's opus 13. Why not play together some bagatelles and a theme with variations? There are lots of possibilities, and of course you must not restrict to thematic recitals. With this sonata also you shall play another ones by Haydn and Mozart. Given the fact that it's a standard, difficult work, your choice of the other two composer may be of easier sonatas. Why not the 545 by Mozart?
Don't worry, because it's really not a problem: it happens a lot. If you want some help thinking about those, I'll be glad to provide some ideas.
Best wishes!