I think you will find your stink is coming from the overflow hole in your toilet. Here's my experience:
I had a Foretravel with that problem and had to plug the overflow hole. That stopped the stink, it was a direct vent to the holding tank. Just had to be real careful not to leave the toilet until it had cycled, in case the water kept coming. The toilet mfg. even supplied the little plastic plug.
In the Marathon, the Microphor toilet has the same vent hole, but there is a small plastic tube that gets a little water each time you flush and creates a mini P-trap. My plastic line was pinched, all the water had evaporated and let stink in anytime you created a vacuum from the Fantastic fan or driving with a window open. Fixed the pinched line and all is well.
I know this is JDUB territory (poop, toilet, holding tank, butt crack, stink, etc.), but trying to help!
By the way, where is the Flame Snuffer, he's missing?