Rid-ich is malachite green, which is pretty harsh and not going to "cure" your fish of ich anyway. It would be better to just leave the fish in copper for 30 days, and then remove the copper with water changes and carbon/cuprisorb after to observe the remainder of your 76-day fallow period, med-free.
You can add CUC/inverts during your fallow period but keep in mind every new addition will re-set the clock (your fallow period only starts after your last "wet"addition). Snails and such can't HOST the parasites, but they can carry them in if they've encysted on the shells, skeletons, etc. Basically any hard surface. Unless they have already been QT'd in a fish-less system for 76 days as well.