I watched your recording and saw a lot of good things! Your snap to knife edge is very good, and your 4-point rolls are good also. You maintain a flight line really nicely.
As for working on what you have already, I would say try to maintain a more flat trajectory on your slow rolls. Instead of pitching up coming into it and allowing gravity to flatten it out, add a slight bit of rudder on knife edge and elevator when inverted, to try to keep the plane flat throughout. As it is, it is sort of like a football where it starts a bit nose up and ends a bit nose down. Same thing with your square loop - when inverted, add a bit of elevator to maintain that flatness!
Other than that I would say add a few more "moves" to your repertoire! From the classics like the immelman or hammerhead to more modern crazy stuff like the aneurism... there are all kinds of cool aerobatics to learn! I won't show favoritism but there's plenty of sites on the web with info.
Overall it was fun to watch! Thanks for the upload.