In general I would have some more rock in there, especially since you are relying on it more than larger tanks with sumps, fuge, etc. I would aim for at least 2 pounds per gallon, I had 3 per gallon. You can add dry rock for about $2/lb and it will become live rock eventually. I would do this unless you cheaped out on the rock you have and still need to get some high quality live rock (you need to have some good stuff in there to bring in the diversity in the first place).
To your actual question, yes, you should be able to ditch the HOB
if you really want to, but it is better to have it and maintain it properly than just to ditch it.
If you can keep up a good water change schedule on that tank you don't need a skimmer, but it is a good idea to have one. If you decide to get one do not get a nano skimmer or one rated for your tank, you would want one rated for much larger. A small HOB
would be fine, even a Seaclone would be beneficial.