Dwarf gouramies are fragile and very easily get stressed. I wouldn't put them in with naything likely to breed and be territorial - so no to the firemouths and no to the kribs (though this depends on tank size). I'd also probably go against the keyhole idea though keyholes have always been extremely peaceful IME and should in fact be ok as long as the tank is planted well and large. Platies are fine. I'd say no to mollies because I've never had any get along with any type of gourami and they do better in harder water anyway.
Try getting a trio of banded gouramies (Colisa fasciata) instead. They grow to 4" and look similar to dwarfs but are far hardier and sturdier. I'd still skip the firemouths.
