Glav,
Yes MDT's have a gcvw limitation and it should be a part of the truck documentation and posted on the truck.
As to the second question. I'm not sure if you are just asking for the current weight of the vehicle you wrote about or are asking what the max weight would be. The axle weights you listed shows the truck weighs 15,000 lbs. at the time you weighed it. It does not mean that is it's max weight. The factory determines that.
Just a comment. Considering 300 lbs for "weight transfer in braking" is a very miniscule amount. The weight transfer will be far more than that, but I believe the manufacturer took that into account when they designed the unit. Otherwise we would see vehicles broken down on the street all over the place just because they hit the brakes.
