I would return the gourami. You don't mention the species, some can be very aggressive, and interaction between them is to be expected but it could be nearing real trouble or not, depending. Gourami and cichlids should not be together in the same tank, primarily because they are so much alike in temperament and territory defense.
Five or six angelfish is advisable, four might be lucky and work or might not, depending upon gender and temperament of the individual fish. Provided you have not had the four for long, adding two more might work out fine.
Back on the Quikrete Play Sand, that is excellent sand for tanks. I contacted the manufacturer a few years ago to discuss their processing. I have been using this ever since, with no problems. I have the dark grey sand in the local Home Depot, there is also a buff-tone sand. Either is fine, Quikrete Play Sand.
Rinse it a few times. I never go overboard with this, as it is just dirt that will settle.