Welcome to the forum !
With your numbers:
14,000 GCWR - 6,500 actual TT weight = 7,500 is the max your TV can
weigh using those numbers
If you load up that trailer to it's max rating of 7,500...this is how
much your TV can actually weigh fully loaded
14,000 - 7,500 = 6,500
Forget about 'dry' and 'MTWR' (your tow cap)...they are marketing numbers
derived from a stripper model (AKA...curb). Unless you own a stripper,
they do NOT apply to you
6,500 actual weight of the TT and a 645 tongue is not good. Tongue
weight should be about 13% or 12%-15% of the actual weight. I prefer
closer to 15% if your TV's RGAWR has the capacity, but most half ton
like yours has an approx 4,000 RGAWR
Best to load up your TV ready to go camping and then actually weigh
your TV, axle by axle. Then do the simple math
Ditto the trailer, but if you haven't purchased it yet, then I suggest
using it's GVWR as that is the heaviest it is rated for
Post back your actual weight numbers and F/R GAWR for further assistance