Goldfish grow too large, they are very social fish that need to be kept in schools so they need very big tanks, proper filters, they're messy and need plenty of water changes, that is not the type of fish we recommend to folks coming here. As you have seen on the Injaf page, there are other fish that look just like goldfish such as rosy and golden barbs that stay small and are easier to keep. On top of that, we don't really recommend deformed fish like the fancy goldfish or "balloon" varieties because of the problems these fish go through.
That is a tropical temperature. Meaning you would be able to keep most tropical fish without a heater.
There seems to be no change in either of your readings, have you checked whether the Stability is expired?