FWIW, I'm 6'5" 260 and rode a soft 164w Burton Bullet for my two seasons without too much of a problem. It would wash out a bit when I started riding faster but it was fine. That board is much softer than the 164 you bought, so I'm guessing you'll be fine. If you start going too long you might have issues controlling the board as a novice rider, but hard to say for sure. I'm now on a stiffer free ride board that's a 166w and don't see myself going bigger anytime soon. It's perfect for me and the places/conditions I ride.
Drinking the Kool-Aid:
NS Heritage 166X