You are fine, there are guys who cook their briskets at 300F and up, even at 350F at times. It will be done faster and once it hits stall, it will come out fast and rise fast. You will need to pay attention at 180 or so to the stall and when it comes out.
BTW, 160F does not mean you are 3/4 of the way to done time wise, you are gonna hit the stall and it could be an hour in stall before it climbs appreciably. It should hit 165F for a while, even an hour or so, then it will climb to 190 or so, that is when it is getting within an hour of being done. But, it could be less or more on a gasser if it isn't holding temps below 300F
me: I don't drink anymore
Yelonutz: me either, but, then again, I don't drink any less