Pyro already answered the tally question. As for using him in a chaos marine army. Yes you can use the model, but no you can't use the rules. Now if your opponent agrees, then all that goes out the window.
The true man wants two things: danger and play. For that reason he wants woman, as the most dangerous plaything.
No, he is for a Daemon army only..He has to be spacifically listed in a chaos space marines codex for u to use him or at the bottom of his stat sheet it will say "for use in a chaos Daemons and Space Marines Army" as it states for most models in the Imperial Armor Apocolypse books.