As other people have said, it looks like you have good speed and power, and it is interesting that you chose footwork to look at for improving. IMHO, footwork is one of the most important things that people tend to over look. Good footwork (not fancy footwork) improves more things than I will spend time listing here. Personally, I think you may want to try this:
* Not sure if you were wearing handwraps, but, if you weren't, get yourself a good pair of 180" Mexican style wraps, and wear them every time you work the bag. Your hands will thank you for it in the long run. Trust me.
* It looks like you have room to get that bag off the stand, and ceiling mount it. Do it, so you can work around the bag, and remember "work the bag, don't let it work you."
* Check Youtube for some free footwork tutorials (everything from basic to advanced), just remember, there is a lot of crap on there also. Some of the stuff from Title Boxing that people put up is decent.
* Buy and set up a double end bag. They are cheap, and will improve your footwork, as well as your speed, timing, and accuracy.
**** Footwork puts you in range to correct a whole host of problems, from arm punches, getting in and out of range for throwing punches, avoiding taking punches, and getting the maximum out of your punches. Everything else can be great, but if footwork sucks, nothing will work like it should.
* Try using a double jab as a "ranging" punch. Once you are getting good hard pops on the bag, and your footwork is positioned so you are not over or under extending your reach, that will give you the proper distance, and then continue to use your footwork on a moving bag or target, to put you there.
* Try stepping in prior to throwing combos, and stepping back out or angling off when you are finished, and work your stance accordingly. Don't bounce up and down, it is totally fruitless. You can't throw and land a power punch, take a punch, or avoid a punch, when both feet are off the ground for that short period of time. A skilled opponent will pick up on any pattern to the timing you use to do it, and capitalize on it.
I hope this helps, and good luck!
:icon_chee