Hi instromp,
zheer gives you some good advice, particularly on dynamically layering the different voices. This is a more sophisticated step beyond simply balancing the hands. If you study the form, away from the piano as zheer suggests, you'll find that this middle movement actually is very similar to a string quartet, and takes on that characteristic in the playing. So you have to think instrumentally rather than pianistically in rendering this piece. Right now, you have the notes down for the most part, but there is, at the moment, more focus on articulation more than anything else. That needs to shift to producing a long, singing line--often representing the violin. But occasionally the viola or cello takes over, and comes to the foreground while the violin retreats to the background for a bit. So you need to work at producing a rich, adagio, legato, cantabile sound, where the melody is always clearly etched, while accompaniment is background only. I agree with zheer too that often the bass becomes important in supplying a moving harmony. In part B of the movement, there is some excitement, but otherwise, this is a gently flowing string quartet.
There are moments when you can make some nice melodic nuances, and I would encourage you to consider doing so. These are done by using very careful and judicious rubatos in good taste. Bear in mind, though, this sonata is early-period Beethoven. He was indeed a precusor composer of the Romantic Era, but much more so in his late period. So you cannot exaggerate any rubato effects here. This is not Chopin. I hope this helps.