Good idea to get the diet and exercise under control and then focus on stress later. Many of us find this helps enormously with symptom management and once diet is under control then the negative effects of stress seem to be lessened too.
Later if you need a stress reduction technique you might try the gut directed hynotherapy which has been shown to quite effective for some people. Heather even has board dedicated to hypnosis for IBS.
I will answer you other questions in the posting you made with questions directed to me.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS