I can definitely breed Justified, but Justified is a Dream World ability while Zen Headbutt is a 4th gen tutor attack. You'll have to pick one or the other, and honestly, I would prefer breeding Justified.
You should in a sense. You see, downloading a Pokemon directly from Pokecheck will attach a ribbon to it which does make the Pokemon illegal/hacked. You need to download the Pokemon as a .pkm and use another Fake GTS program to send it to your cartridge. I wrote a short guide on it you can read here
Hi, thanks for the PM. Glad to see you're enjoying Pokecheck! Yes, all of my Pokemon are legal, however, a few malicious souls have edited my Pokemon and put up hacked versions of them. This only a case for like, 1 every 100 Pokemon though, so you should be fine. I can guarentee the legitimacy of any Pokemon with one of my OTs when "Owned by the registered original trainer of this Pokémon." appears in the legality analysis. All of the Pokemon on this list should have that and are uploaded by yours truly.
By the way, are you querying Pokemon directly for download from Pokecheck or are you exporting them as .pkms?