You're doing awesome, you're definitely getting there. :) It's not perfect yet, but it's a definate improvement. Much less pumping, and though you still do it a little bit, your canter is starting to look more natural.
The next steps are to take a look at your elbows and your shoulders, and see what is happening. Though you are making an great effort to still your upper body, you are still somewhat pumping with your elbows. In other words, in your attempt to go with your horse's mouth, you bend your elbows and then snap them back. This pushes your shoulders and upper body back and creates that rocking/pumping motion. So instead of doing this with your elbows, try to only lightly go with the mouth and gently move your hands.
I would suggest practicing riding in half-seat. When you do this, keep your upper body completely still, stretch your heel down, and absorb the canter in your legs. Keep your shoulders firm and watch your elbows. Also, here's a little trick: tighten your abs while cantering. This helps keep your back firm, absorbs the motion, and stills your body.
On a whole, just remember: be gentle with your elbows, and use a nice quiet half seat. Other than that, I think you're doing wonderfully. Lot's of progress and a great improvement. Good luck, and keep at it. :)