I would say, considering your water parameters, tank size, and the condition of the fish, i think you should take the fish back to your LFS. The pigmy angel fish you have needs at least moderately good water conditions, a varied diet, and most people would recomend at least a 30 gallon tank to keep these guys healthy. I'm sure you could do it in less, but right now your tank is quite unstable, and I would guess its at the very least going to shorten his life considerably with the ammount of stress he is going through. Dont worry thought, the LFS will most likely take him back redily. I would wait to your ammonia and nitrites get back to zero before adding any fish. Or if you cant wait, go with something really hardy (and inexpensive)...some sort of damsel to see if your tank (and you) are ready for a bigger challenge. Good luck, and hope your tank turns out beautifully