I used QuICK cure and my shrimps and frog survived the regular dosing. If you want to try this, I'd recommend using half the dose, I think the frogs are sensitive.
Anyways, not sure if it's safe for frogs. BUT, since frogs cannot get Ich (or so I think), then you could remove the frog while you treat the ich. All the ich in the water with the frog will be dead from not having a host by the time you finish treating it. So that's one option.
If you do decide to use QuICK cure or any other medicine be sure to remove your activated carbon.
Lot's of people would recommend the heat treatment though I'm not a fan. Salt is another option that you can add temporarily though I'm not sure of how the frog will do with it.
Water changes may help as well, because poor water quality can bring about stress to fish, and stress is the cause of ich. Healthy fish can usually fight off ich and won't get it. Also gravel vacuuming can be helpful when you have ich.
Feeding less/more won't matter to the ich, unless you are overfeeding, which could be causing poor water quality.
As I said, stress causes ich. Try to reduce the factors that might be causing stress to the fish.