If you recheck the specs on the one I listed you will find that it is rated for 39.6 - 79.2 US gal./h, also check the dimensions and you will find the one I listed is very small which is very important when you only have a few gallons to work with. Another powerhead that I didn't look for a link for that has about the same specs is the Zoomed 104. By no means am I saying you have to use the links I give, they are mainly for reference. If you were to shop around you may find the same items I link cheaper, the links are mainly for illustrative purposes.
I think you are on the right track for cleaners. I say a couple of nassarious snails forthe sandbed, 2 or 3 blue legs, and a couple of whichever snail you like for the glass and LR. I would avoid turbo snails though, you will find that they know stuff over all of the time in a small tank. I really like cerith and margarita snails since they are pretty small and get the job done. You may find you need a few more cleaners of one kind or another but start off with a couple of each and then add as necessary so you don't have cleaners staving due to overpopulation. HTH, Skip
PS I just looked at the powerhead link I gave you, take a look at the customer comment made near the end of the listing.