Burping Up Food. Throat Closing Up. HELP/ADVICE?

I don't recall your saying whether or not you were titrated in a classic sleep study. It's not a complete answer for your issue, but if they can duplicate in the lab what you experience at home, knowing what pressure is recommended can certainly help. A constant pressure may be better for you, if you find the right pressure. Are you using sleep mapping software? Do you know if you're having unusual obstructions or episodes while sleeping? If your esophageal sphincter is to blame (and forgive me, I may have missed your diagnoses regarding this), there's a laparascopic surgery that can help. I hope your scheduled sleep study provides useful information. Sometimes a respiratory therapist has more insight than a doctor.

I was warned to avoid benzodiazepenes and pain meds hours before bed, as these all repress respiration. This can include pot and alcohol, of course, strong muscle relaxers, sleeping pills, etc. Combinations of drugs. If you're taking painkillers, for instance, your breathing may be deeper and more shallow; if you use variable CPAP pressure, it may be kicking out more pressure when you don't need it, leading to excess air at times, and not enough air at other times. Apparently, our bodies become more sensitive over 50 (if this is you), and even a small amount of medication can have a negative effect on respiration during sleep. You need a good respiratory therapist and lab measurements to pin this down.

Are you certain what you have -- OA, CSA, or both? A proper diagnosis is imperative. If you self-diagnose and try to treat yourself (as many of us do without proper insurance), it can be problematic.

Do you have allergies that could be treated? (Beware any meds that affects respiration later on in the night.)

Is there a dental device that can keep the air from rushing down to your esophagus? I know there are mouthguards and orthodontic devices that fill the mouth, but don't know whether this would be enough to shape CPAP airflow. Perhaps ask a dentist?

I sympathize. I know this set of circumstances is distressing. The only thing I can suggest is persistence. I think the default mindset of medical providers (even specialists) is to shove us out the door. (And if they had to live with something, they'd try a lot harder to figure it out.) -- Good luck.