H pylori does increase the risk for cancers in the stomach. Eradication however, is feasible for this risk factor so this is a good thing. The presence of Crohn’s disease also increases risk and is a function of duration of illness. If you only have pre-Crohn’s features, then this situation may not increase the risk as much. If your grandma got colon cancer after her 60th birthday, this is usually a sporadic case more than a hereditary case. Since you have polyps, it would be good to keep to the schedule of follow-up. Aside from this, maintaining a proper diet and exercise would be good for cancer and for general health as well. Discuss your concerns with your doctor. Stay positive.
If I have "pre Crohns's" will I sooner or later develop full Crohn's? My grandmother was diagnosed with colon cancer when she was 59, she would be 60 next month. But with the Crohns I had another grandmother and uncle die from it. I was told that my uncle was the youngest child in the US to develop it, there where no medicines to help him.