I think we should slow down a bit.
You're currently at the fish store getting your water tested? Lets see what results you get from them; we can go from there.
No, I wouldn't try to feed it in the current state. It seems stressed. When was the last time you were stressed about something and was able to eat? ;) So no, don't feed. They are filter feeders, so, it will pick up some nourishment along the way.
Also, I think you should stop additives temporarily. Lets check your chemistry and make any necessary adjustments before we begin adding any product to the tank.
Also, I would set myself up with a water change station. It doesn't have to be big. 20% of your tank's total volume is between 2.5 and 3 gallons. I've always relied on 20% weekly water changes to keep my small tanks stable.