My wife and I are taking delivery of a 2016 Cougar 333MKS. This will be our first 5er, and an upgrade from a 2012 Trail-Sport 27' bunkhouse TT. Current TV is a 2015 Ram 2500 CTD/auto, CC, 4x4, SB, ...
Keep in mind that the 60 gal fresh water tank is in the rear, well behind the axles, so a full load would not adversely affect your pin weight. That might help your rear axle calculations a little bit.
I tow with an F350 with stock braking and wouldn't want anything less in braking power. Some drivers have put those brakes to the test for me on several occasions. The 333MKS brakes are OK (typical) but maybe a disk brake upgrade might be useful.