The only thing I can contribute to this thread which hasn't already been stated (even though its mostly a reminder to what has already been discussed) is that a SW tank cannot be stocked like a FW tank would be. Even little fish like the firefish should be given something like 10g of the total tank volume just for themselves. Especially with so many large fish, several fish which rely on copeopods as a food source, and how new the tank is... I myself would not have so many fish in the tank. I'd probably not have many more than 5-6, depending on their size. To reiterate something which has been mentioned a couple times already; we should stock our tanks based on the ADULT size of our fish, not just their present size. Stunting our fish, though we can't actually see its effects until the fish dies, is a painful and cruel punishment to creatures which cannot do anything to fend for themselves beyond what we allow them to. We control every aspect of their environment, and as such, we should be diligent to do everything we can to provide them with the healthiest environment possible.
Now, I will give you the ability to refute (to a degree) what I just said. I keep my 55g FW tank fairly heavily stocked. See the inhabitants in my sig. I work VERY hard to try to keep them happy, but I can't help but to feel guilty for not being able to provide the discus with more room. Is a 55g adequate for 6 discus? Some say yes, some say no. Opinions are like elbows.... everyone's got 'em. Ultimately, no matter what opinions we share on here, you will have to make your decisions as to how to care for your tank.
If I could offer any one piece of advice right now, I'd suggest not worrying about adding fish at the moment, but doing everything possible (including daily w/c's if need be) to help alleviate the ich issue in your tank, and help get your fish as healthy as can be before adding anything else to the tank. I certainly agree, adding chemicals is usually not a good idea, for if it its able to kill one living creature, it must be able to do at least some damage to another living creature... its not inert stuff. Perhaps do some reading on treating with hyposalinity? I've never tried this, so please don't jump into it without a LOT of research, as it may be more stressful than its worth, but its at least worth a read. Best of luck to you bud.