1: Tapwater: more than likely when you boiled the water, all the chlorine was boiled out https://aquanswers.com/does-boiling-water-remove-chlorine-chloramine/
Yes, it is absolutely better to use filtered water for your brew, but if it’s coming from a reliable municipal source, it’s also almost never a brew-killer. Depends on the strength of your culture, but if you bought your scoby from us, it shouldn’t be a problem. DON’T WORRY!!!
2: Scoby growth: the scoby will NOT stop growing…however, that first layer may sink to the bottom and another one may take it’s place. If the baby scoby stops growing, it could be an issue…but it could also mean there’s just not enough sugar left for it to eat. If it was doing well before, it should be doing fine again.
If it were my brew, I’d finish it down to a pH of 3, save 20% of the liquid, and start another batch with it. Your 2nd batch should come out pretty well perfect if you leave it alone…even if you use some of that good KC tap water!