Good morning I will try to help where possible!
DEF approx 1 gallon every 500 miles that's with a 450 ISL Cummins
We have a 90 lb. Golden 75 lb. border collie, we cover the couches. IMO fabric material and the ultra leather wear about the same, that's why we cover!
I am sure the chassis manf, most likely freightliner Pairs the tranny with torque
I would have Tiffin install your dish, this will be an upgrade
The TV's are all HDMI in today's coaches, not sure on the blue ray?
Do yourself a favor get the dual pane windows help prevent a lot of condensation issues
In our coach we have a separate 2k watt inverter it runs off its own bank, don't know about charging them with a separate generator it has never been an issue.
The size of the night stands are reduced, no problem. IMO the advantage of the residential refer was a major factor in our purchase!
The al rims not only look good but hold up excellent, when we traded our 03 Excursion they still looked new.
The keyless entry can be purchased after market, if you desire this personally I would have Tiffin build it
Tiffin is still in business, Nuff' said!
Cummins is an excellent engine, we do not change the oil as it holds 25 quarts, I do change out many filters on the coach, just depends how the chassis is laid out.
Have fun and enjoy your new coach!