For cards that say "if you control X character" or "for every X character you control". if they are stunned, do you still control them?

Yes, you do.

That's why many of those cards say "a non-stunned character you control" or "a ready character you control" since stunned characters are never ready.

Does this mean Cosmic radiation would ready (and by virtue of what the ready status is, recover) stunned FF characters you control?

The text is: And you just said that a player controls all of their stunned characters... seems kinda strong :(

No, you can't ready stunned characters, so while you can choose them with Cosmic Radiation, it will have no effect. Cosmic Raidiation is NOT Children of the Atom on steriods.

Oh yea that reminds me I have to remind my X-Men opps that RECOVER from their Children of the Atom does not READY their chars ;). And they whine about it like well then what's the point. Always have to point it out in the rule book to prove it too. :P