I'm sorry.
It's very frustrating.
I am most confident of the efficacy of a 10% clorine bleach solution. I'm not sure myself of the substrate, although bleach will cleanse it too. After, rinse everything well and dry in the sun. It will destroy all nitrifying bacteria, I'm afraid, so it will need recycling. As far as destroying the ich parasite, that is never, as it is present in all water but maybe IO or some such, even then... Ich parasite goes through several life cycles. Its like trying to rid your carpet of all the mites.
In reality the ich parasite requires a host fish to maintain it's cycle. So simply letting the tank dry out and not using it for a few weeks will throw the parasite into a dormant stage at the least. Since there was some suggestion that more might be afoot and behind the infestation, a thorough disinfectiong might be in order.
If you do run the substrate through a bleaching then perhaps a complete soak in declorinator would be convincing. Actually a complete rinse and dry out should eliminate the clorine.
I have to disinfect a 25 gallon tank of fin rot bacteria. I am assuming that I must disinfect everything including the bio wheel, decore, and the substrate.
Clorine oxydizes in the sun and air=it burns up. That's why it is considered a good disinfectant. It burns all the buggers up. Remember there is clorine in most water supplies, and we simply let the water sit for 24 hours to naturalize it or we treat it with declorinator.