First yes Healthy fish can get ich, and that has been proven many times over. Once again unless you have a huge tank all fish are stress to some point in our home tanks. As for being in breeding condition, that has nothing to do with a fish ability to get ich. It's very common to see fish exhibit signs of breathing, from clean off rocks to doing mating dances, but those very same fish can and do get ich.
Yes ich is a parasite and they attack all fish, not just fish that are sick and dying. Fish that are sick and dying will most likely die from the ich, as opposed to a healthy fish that has a better chance to fight it off, but there is no guarantee that will always be the case. As for seeing fish swimming in the ocean, well they maybe less stressed than fish we have in our current tank, and in breathing condition, but they're full of parasites and diseases.
As for Hypo or Copper both take a while to work, neither is faster though you have to treat with Hypo longer. Remember Ich can take anywhere for 4-7 days to work it way through the fish body, and copper doesn't have an effect on the ich inside the fish body. So it may seem like the fish is doing better it's just because the ich hasn't reached the stage were it has worked it's way out of the fish body. There are also strains of ich that are resistant to copper, unless the levels are so high they'll kill the fish.
As for using quinicrine hydrochloride, well I never have but I serious doubt it would kill all the ich in one day without killing the fish, then again you made a similar claim about copper also. The other side is if it was that effective everyone would be using it and that's not the case.
Here is an article on using quinicrine hydrochloride
http://www.marineaquariumadvice.com/aquarium_fish_4.html
ntimalaria Drugs
Several antimalaria drugs have been used with some degree of success for combating
Cryptocaryon irritans. These would include, but are not limited to, chloroquine phosphate, quinine hydrochloride and quinacrine hydrochloride (Atabrine?). A bioassay should be performed before using antimalari drugs, because their strength can vary greatly from one batch to the next. In my experience, quinicrine hydrochloride was partially effective, but problematic. This treatment caused some of the fish to take on a yellow hue or darken in coloration. It also appeared to cause the fins to begin to fray at about one week into treatment. The recommended treatment period when using quinicrine hydrochloride is 10 days, which is not generally a sufficient period of time to eradicate
Cryptocaryon irritans.
Ich maybe a parasite but I don't think it's the same as malaria, which is I think a worm parasite while ich is a crustation type parasite.
Paul I really don't care if you like me or not but don't put information here that you think is correct when it's not. You have a lot of newbie here and you putting information this some may use which could lead to them losing a lot, or even all of their fish.