Slow digestion is consistent
with a sedentary lifestyle. I'd suggest you walk or do other exercise at least 30 minutes a day to raise your heart rate at least 30 beats per minute. You mention you have diabetes, and if the 300 rating is from a fasting test, that's totally out of line.
I would take a Proton Pump Inhibitor and mix in daily exercise, eat foods with fiber, stay away from the inside of the supermarket, buy the vegetables, etc on the perimeter.