I have crohns but was not due to the MJ, neither is your IBS. IBS and Crohns etc are a result of your parents vaccinations when they were younger mate.

Quitting weed will not solve your stomach problems at all, however if you think it will then go ahead and try. You will be better off with aloe vera juice which I often take.

I did give up smoking MJ for around 6 years or so but started again and have one or two smokes before bed to help me sleep.

I have been smoking weed on and off for 25+ years, never ever had a problem.