Hm, you are correct, the spelling is Bodhisattva, although you must admit it's a pretty easy word to get wrong. Fifth, as I had thought him up, would have Flametongue (Native), Old Realm (dealing with Spirits), Riverspeak (Sorta gneral tradespeak, plus he's close-ish to the Scavenger Lands), and one more, either Low Realm or the language of wherever we're going to be playing. Also, though Fifth has great love and respect for his country (as reflected by the Intimacy), he is not truly welcome there, and, in any case, his quest for realigning Heaven is more important to him than his country. Plus, the Wyld could have left him just about anywhere, after so much time. Waypoints change location with frequency, and his Exaltation could've really happened in any corner of the world. He can fit nearly anywhere... after all, his greatest secondary theme is travelling.
As for knowing the other characters, it's possible, though personally I would like to play out his joining the Circle. It's no problem if you want everyone to know each other for purposes of streamlining everything, though. Fifth is relatively trusting of other Solars, as he considers them potential allies (after all, his goal is for the betterment of all Solars, even though his reasons for it are personal), so it'll be pretty plausible for him to team up.
About the Lunar... I dunno, I guess if he really does have an amazing concept and it seems like it'll be fun ahving him in the game, then yes, but we do have a Perfect Circle here. I'd actually prefer another Solar, as a Lunar has a high possiblity of either becoming "that other Lunar" and not really being special enough, or forcing you to throw in challenges that should be solved by shapeshifting, which means the rest of us don't have much to do. Your decision, though, I certainly won't complain whatever you do.