Agreed, no point separating any fish now as most have it already. Someone else will no doubt be along to advise you about using No.6 and whether to reduce dosage for your clowns as I've never used it. I use Protozin for white-spot and swear by it. Have you added any new fish recently as that's usually what causes white-spot?
Your tank is over-stocked! You have 54 fish in there, all small-ish but they'll grow. Why do you only have 1 cardinal? They should be in a shoal of at least 5 or 6 and not really mixed with neons.

Oh I live in London and the product isnt avvailableI really wouldn't bother separating them- I don't think it will make any difference as the Ich is already in the water. I treat it with eSHa EXIT Anti-Whitespot treatment, and it clears it from my tank in 3 days. I have guppy fry at the moment and I was treating the water when the mum gave birth to them, and they seem to be fine, so I wouldn't worry about the treatment affecting them. It should clear the tank from it, but I only know that the eSHa EXIT treatment definitely works- yours probably will too.
Oh I live in London and the product isnt avvailableI really wouldn't bother separating them- I don't think it will make any difference as the Ich is already in the water. I treat it with eSHa EXIT Anti-Whitespot treatment, and it clears it from my tank in 3 days. I have guppy fry at the moment and I was treating the water when the mum gave birth to them, and they seem to be fine, so I wouldn't worry about the treatment affecting them. It should clear the tank from it, but I only know that the eSHa EXIT treatment definitely works- yours probably will too.
good luck!
As you've been told before you don't have a filter that will cope either.