Well, I think once you entice him to eat you can change his diet. Go to the supermarket, get some raw shrimps and chop them, if he eats that he will start eating other things afterwards. Alternatively your LFS might have the artemia.
The only other prestuff you can try is flakes but if he does not take them and you do not want to try anything else I would recommend taking the fish back to the store before he gets weaker.
jawfish really aren't suitable for a "pellet food only" tank. They are shy, picky eaters that are difficult to even put on a frozen food regimen. When say "mix stuff" for corals do you mean the liquid Microvert-type foods? If so, you ought to toss those out and use a good frozen food for everything instead. All they are is bottled detritus-- essentially dumping pollution to your tank.
crhis may have been a little more blunt than needed but don't ignore his underlying message: If you are not prepared to give your reef inhabitants what they need to THRIVE (not merely survive) than you might want to reconsider your commitment to this hobby.