Your symptoms seem significant, you have had them for 15 years and they are getting worse. I think the solution I use (diet - all aspects of food) may be something to try before surgery, and if you go the surgery route, get a gifted surgeon - check out doctors recommended by top doctors you know as well as the Castle and Connolly website. They research each listed doctor to verify their excellence; they don't charge for this; they make their money another way. Google the site and see for yourself.

I have a much milder case than you do, but several other gut problems too.

I have a severely redundant colon that slow motility and causes constipation.

I solve my milder problem by eating soups with well cooked veggies or that are pureed. I eat hot cereal once or twice a day. I have "regular food" once a day. Soft, moist foods are easier to digest. Little meat and fish. Almost everything is cooked (which makes it easier to digest).

I drink a lot of warm drinks as well as cold milk and I try to sip water all day, all to keep things moving. Peppermint tea relaxes the gut. I drink it for IBS-C but it may help you too. Heather's Tummy Care sells an awesome peppermint tea in bulk purchase form.

If you give your gut soft, liquidy food that can move through your gut's twists and turns easily, that would be something to try before surgery.

I have read on this Mayo site that some surgeries of the gut work well, but some create adhesions (scar tissue) that can also restrict gut movement and digestion. Hence the need for a gifted surgeon if that is your best or only route to improvement. If it turns out how and what you eat doesn't matter, I would consider surgery if I were in your shoes, and I would find a gifted doctor.