Sorry bro, but it is possible to win chess in four moves, although not against a player with any ability at the game, which Gaunt probably would have. As to the rest of it, a little far-fetched, but there's nothing saying that they can't be 7ft tall, Bragg was probably that tall. Although he does seem a little overloaded with equipment. Also, in terms of having once been a Commissar and now being a Colonel, he can do that, Gaunt was offered that himself, to be raised to General I believe? but in so doing giving up the additional powers granted by Commissar rank.
The rest of it seems sound, prehaps a little more detail, welcome to Heresy mate, interesting that you've decided to go straight into GM'ing an RP, I'm currently engaged in far too many, on this and other sites, to join but good luck. I may very well watch from afar.