Hey WJF, I'm completely down to be your test subject and offer any advice that I can.
Locust pose for Yoga always gets stomach gas moving upwards for me (laying on your stomach, then using your back to lift up your arms and legs;VIEW IMAGE
Even if I have a bit of discomfort before I go to Yoga, it goes away over the course of the session, possibly because of my mind being occupied/cleared and also the cool-down relaxation at the end (approx 10 minutes of laying flat on the mat and clearing my mind). I practice Birkram Yoga. I think you might be onto something with the breathing as Yoga also focuses on the breathing patterns very closely.
Sauna knocks it out for me (literally) every single time
. Just a couple of minutes and it's out like a light. I can't explain it. I only get to go once a week but I look forward to it so much!
Taking walks doesn't kill the pain for me, but it makes it better while I'm moving and doesn't make it any worse. Plus, I'm burning calories and doing something good for my body. The pain will not win! I will only make myself healthier! Mwahahahaha!
Also, here's the wackiest thing - sleeping on my stomach is the ONLY position I don't get any reflux. Even sleeping on my left side causes it (a classic position for stopping/abetting reflux). If I don't sleep on my tummy, I get that gnawing/empty feeling others have described. Just goes to show how unique we all are :)
Best of luck, hope something here helps you!