Assuming the white spots on your fish is "Ich"..
1) LFS usually use therapeutic copper in their tanks. It suppresses white spots so you may not see it in the tank, but usually does not not kill it totally. Even other reefer's tank may have itch, but because fish is healthy, can fight it off.
2) Yep if your fish is healthy and no stress, should be strong enough to fight it off. But your tank will forever have white spot parasite unless you keep your tank fallow for something like 9 weeks?
3) You can try polymedic as above. Most people says they are reefsafe, but I've read other forums not 100% success. Some use UV. Or both polymedic + UV together. Some people like to add "vitamins" to dip their food before feeding, eg. vitachem. Not sure if it really works, but at least shouldn't harm anything.
Ich is not so scary, just try to keep fishes healthy. Velvet on the other hand..