Your fiance is very smart with the poking of the hole in the squirt bottle, but he's fighting gravity, and gravity always wins.
The Sinus Flush uses gravity. It sounds like he has an anaerobic bacterial infection (I've had similar problem), and it should be treatable. Don't do it for more than 2 weeks to let all the good bacteria grow back. If no success, Google the word "Phantosmia" to look for other causes.
http://www.medhelp.org/user_journals/show/2322
The Flip-Turn Sinus Flush is mildly risky, because you have to bend over to do it, preferably in a shower, but you can also do it outside on soft ground, or you can kneel down and lean over a bathtub with the shower running.