I like your plans to not go crazy on the fish list and great inentions for making more space for them, but still a few comments to share:
Tang Police!
The Tomini, being a Bristletooth (usually a loaner vs schooler) and a relatively small tang, is definitely one of the best Tang choices for an aquarium. He will outgrow your 55, and end up an unhappy fish however - that's only four square feet of space no matter how you slice it!
If you don't have pretty solid plans for (and resources to enable) a tank upgrade to at least a fairly large 4' tank in the next year or so, I would still make another fish selection from other than the Tang family.
Firefish
I would also think long and hard about that Helfrichi.....very expensive and a likely jumper. The common Fire Fish comes with a price tag that is smaller by an order of magnitude (!!) and still has great looks if that's your kind of fish. (Still a likely jumper IME....get only one for safest results.) Stay away from serpent or brittle stars with any of these fish (or really any fish that sleeps in a cave, nook or cranny.)
Clowns
Hard to go wrong with clownfish. Something to keep in mind is that if you like 'em enough you could go with a colony of them so you wind up with a female and harem of males.
Good luck!
-Matt