Stress Coat is fine to use, go ahead and use it up.. Tetra AquaSafe, or Prime are really good.. as long as it removes chlorine/chloramine, ammonia and if possible, binds metals.
How big is the tank? And might as well leave him in there while it cycles, as it can take a month or more to establish a proper cycle (if the tank is large enough 5+ gallons). Just check the water chemistry a few times a week for the next 4-6 weeks, and if you see a spike in ammonia/nitrates/ites then do a partial water change. But the tank will cycle with him in it.