The white cloud could be precipitation or a bacterial bloom. I'd mostly ignore it for a while, but I might so some small water changes, maybe 10% once a day, to remove some of the nutrients or cloud, if I had the energy.
I'd wait for a week of zero ammonia before adding any animals. That gives the tank time to finish processing any continuing decay, and for any possible secondary ammonia spike to happen. I'd definitely do 10% changes at the zero ammonia point for at least a few days.