With 3 kids and a dog add 1500lbs to the dry weight. You can safely tow a 28ft TT with a properly setup WD hitch! The Durango is low and has a decent wheelbase. There is no length limitation in the owners manual or anywhere for that matter other than the state or national 65ft total limit!
I would start looking at a bit longer trailers. And as long as the loaded for travel weight is at or under the weight rating you stated it doesn’t matter if it has a higher GWR. My old TT had a 4100lb CCC. I was always 2000lbs less than the GWR.