Dottybacks can be pretty aggressive, so it should be able to take care of itself against fish equal to or a little bit larger than it.
I'm not familiar with a McCosker wrasse, but wrasses, in general, get bigger than a 40g can hold. Plus, they'll need a sandy substrate since many wrasses like to bury themselves in the sand at night. And I do believe flasher wrasses get their names because they like to "flash" or rub, against the substrate.
You will find in the marine world that stocking size (inch per gallon and whatnot) is not as forgiving as in the freshwater world. IMO, I would say you're at capacity, if not a bit overstocked.
As for the clowns, unless they are male and female, one may harass the other to death. They belong to the damsel family and pound for pound one of the meanest fish on the reef.
How is your tank setup? Live rock? How much? Corals? Filtration?