I'm towing an outback 295RE, similar length, similar weight towing with a 2500 cc duramax. Tongue weight empty was 700lbs. Loaded up tongue weight w/o any fresh water 1250lbs. With full fresh water 1400lbs. I think you'll end up in similar territoy.
next thing, with 7000lbs empty on the truck, with the trailer loaded up, DW, DD and 2 grandkids, and stuff in the truck bed we are at the truck GVWR of 9200lbs. Same with me DS, one dirtbike and some firewood.
I think your gonna find that with 6 passengers in the expy, your gonna be way overloaded.
As a comparison, a neighbor with an expy has a much smaller springdale. He's got the expy at the GWVR limit with he and DW and the smaller, lighter springdale. And his comment is that with the softer springs in his expy, it's adequate but not very comfortable drive/ride.
6 people in an expy is about 900lbs + add 1200 on the tongue. does the expy have a payload of 2100lbs???
And don't know about your expy, but neighbors has a WD TW limit on the order of 900lbs or less. your likely going to be over that limit as well.