Your symptoms seem bad. The only thing i got the first few times was a slight burning sensation which stopped after 15 mins or so. after the 4th or 5th irrigation i stopped getting the burning. Actually i do remember the first time was a little painfull.
I was using 15 drops in 700ml of water, im not sure how much your bottle takes, also my irrigation machine produces a steady flow of water and i dnt have water just sitting there.
You should expect alot of mucus the first week or two i was blowing my nose most of the day and expelling it. Now i blow my nose only a few times. The mucus used to be thick and very sticky and now it is nearly what i would call normal.
My bottle actually says CITRICIDAL (34%) grapefruit seed extract, liquid concentrate.
not sure if that means it is only 34% strengh.