You should be good with that. THe watchman will be fine: he'll be happiest in a live rock stack at sand level, so leave him a cave...lots of open spaces in your rockwork. Lay down eggcrate grid first, then base rock (if any) then live rock, then sand. That way things won't move on you.
You're going to need some more snails, likely. And I really don't recommend cleaner-creatures (unless you just like their look) in a small tank, because what they clean is fish, and they can make a bonafide pest of themselves in cramped quarters: they eat the fish's slime, dead scales, etc, and you know what a manicure feels like if the manicurist goes on too long...
I'd go for some micro-hermits, maybe a green mithrax crab (one of the few safe ones), and some turbos, chestnuts, and the like in the snail department, as well as the nassarius (who will disappear under the sandbed.) You may not have enough crud to feed a nassarius at first: you might want to wait 3 months on that species.
Otherwise, you should be in good shape. The angel is less likely to nip soft corals. Your stony coral lps could come under attack. So be aware. Angels usually live by eating bits of every stony coral on a given stretch of reef. With a mile to run, they're actually beneficial, stimulating coral growth, some think: in the limits of a tank, it's a problem.
