Always go by the Gvwr of the trailer which is too much for your current truck. you will easily be overloaded. Also a safe bet to stay within 80% of your tow rating when towing a travel trailer. I have the same truck and would not go over 8000lbs travel trailer. Look into Lance travel trailers they are built around 1/2t towing
Yes after initially stopping completely then rolling up and stopping one or two more times without much or any throttle input the brake pedal would build up and be hard to push offering very little assist. Now after the replacement of my vacuum pump those third and forth brake applies feel more like the first and second.
I did this to my '16 silverado and wow its perfect now really enjoying the take off from a light and ease to keep speed both in the city and on the highway.