Your ich might be stress ich; something like you falling sick if you are subjected to lousy bosses and harsh working life.
Look towards reducing your bioload..
That will depend. Choose the cheapest fish and put it in. Monitor it for a month or two. If nothing goes wrong then put another.
If cannot, drain water and restart.
This hobby is like that. No shortcuts
Don't advise you dry the rock. It will ruin the bacteria. Can consider trying to soak the rock in fresh water or jet it with fresh water or hyposaline the rock
Hmmmm why didn't try epoxy?
Oh well, sorry to hear about your losses big mike. Hope you can come back stronger (:
Anyway another pest polyp to contribute is green star polyp. Don't see them nice nice and innocent. They are disgustingly ferocious ><