No sure why you are using a floor finish on your shelving. Compatibility is hard to guess. Scuff it up with sandpaper, apply a coat of dewaxed shellac and you might be OK (or, you might not, only tine will tell) With all the wonderful non-yellowing finishes available from the likes of Target Coatings (my favorite) or General Finishes meant for furniture and cabinet work I don't know why you'd go this route.

No high quality finishes that I'm aware of are "cheap", assuming you mean less that $25-30/qt.

Oak, like many other woods, will naturally yellow over time under the finish no matter what you finish it with.