I will preface this with im not super experienced and still learning allot but here's what I think. So gourami wise they can be aggressive like their betta cousins, they are hit or miss so that's what happened with the pearls. Removing the sponges does hurt the cycle some but it's more of a set back less of a whole recycle, you could replace them and if they were stored in water and it would clear up faster like putting old media in a new tank. Otherwise if it was fully cycled before hand you probably added too much at once and overloaded the bacteria as long as you stay on top of the nitrites as you are the fish will probably be fine. Timeline guess I'd say anywhere from a few days to a week for the water changes. Im assuming ammonia? levels are fine as well.