Newbie: Towing TT w/ 2008 Toyota Sequoia

The camping bug bit my wife over the summer so we decided to attend the RV Expo in Boston over the past weekend. She fell in love with the 2018 Rockwood 2706WS and after two days of looking at smaller options, we decided the Rockwood fits our family best as the 3 kids are growing fast. I remember looking in my Sequoia's owners manual before the show for the towing capacity and all I remembered was 9000 lbs. Although seeing the GVWR of 8800 lbs for the TT scared me, I convinced myself the Sequoia can handle it as I wouldn't tow with potable water. I obviously should have done more due diligence... So after spending the morning researching towing with the Sequoia, and how to calculate the weights using the TV & TT ratings, the main takeaway from the research is that Toyota has downgraded the max towing capacity of this TV to ~7600lbs applying a new standard (J2807). This has been well documented in other posts. So I've come up with the following calculations for my set-up:



So, sanity check time:

1.) I made an assumption on my hitch weight based on Rockwood's publicized 804 lbs assuming they got that number using the TT's GVWR. Is that reasonable or should I have just used the 804# number?
2.) I did purchase a WD hitch but I don't know the specifics (yet). Do these really weight a few hundred lbs? If so, I definitely need to include that in the calcs.
3.) For the experienced towers/campers that actually weigh their rigs, is 950 lbs. of dry cargo even a reasonable number for a TT this big? I would assume we have to pack incredibly light... and that may be a challenge knowing my wife.
4.) What other thoughts do you have besides the obvious I need to upgrade my tow vehicle? Will do so in time.