In my opinion, you are pushing the upper limits of your truck, both with the length of the trailer and its weight.
Common sense tells us that tongue weight should be somewhere between 10-15% of the trailer weight and that the "wet trailer weight" should be in the range of 75-80% of the tow rating of the tow vehicle, to be on the safe side.
Look at my configuration. Ford tells me the tow rating on my truck is about 8200#. My trailer, when loaded is in the neighborhood of 5000#. I purposely bought a light-weight trailer so I can safely tow it. I considered 7800# trailers and decided against them.
I have found my rig to be a well-matched, easy towing combination that has over 35,000 towing miles on it and I love it.
Paul <?)))>< Lake Almanor, CA
2002 Thor Tahoe 23FBGL TT, 28'