Love your suggestions except

Not sure about coffee... there are 2 popular variations of IBS, 1 type experiences diarrhea and the other type experiences constipation.
Because coffee is a diuretic, it will dehydrate the body. If you are suffering constipation, the last thing you need is further dehydration.
I would suggest aloe vera (inner leaf only) as this stimulates the peristaltic action in the gut

In addition, I have had IBS in the past and I share my experience here if you would like to have a read and provide feedback?