I keep a large 'empty' gas can on board the MH all the time. Even though I do tow a car.
Not all gas stations sell cans and if they do have one my experience was they wanted 50 bucks cash to borrow it for a road emergency Long gone are the days when they would lend you one.. :R
So an empty gas can on board will at least be available for a passer by that might stop to help you get gas since you don't tow a car.
Bringing a Portable gen with when you have an on board gen? Don't really see the reasoning behind doing that. Your gen on board runs off the MH gas tank. all I do is make sure I never pull off the road to park with less than a 1/4 tank of gas so in an emergency I can always use the gen on board.
The ONE and ONLY and LAST time I pulled off the road with around 1/4 tank gas the CG had a power outage.:R
Luckily the big gas tank came in handy to fill up the MH so the gen could be used. Power was out for 3 days do to storm damage. Now I never pull off with less than 1/2 tank in the MH