I can't answer most of your questions, but I do know that a xylitol sinus spray is a safe, natural way to kill bacteria. I actually make my own, but there is a brand called "xlear" that I bought on: http://www.vitacost.com
Actually xylitol in general is a very helpful thing....you may want to google xylitol, benefits/side-effects.
Taking it orally make make your digestion worse, but the nasal spray should be safe, I think.