I don't have the expertise to address all your concerns, but from my experience, there are no one-size-fits-all solutions in this business. You have to address each issue separately.
I too have had problems with air in the stomach. For example, I just got a new cpap machine recently. The old one had been wearing out since last summer. I think the bearings were bad, and it was not putting out the pressure it was supposed to. The new machine was set to the old settings exactly, but it was obvious that the pressure was higher than what I was used to. For the first three or four days I struggled with the painful bloating and gas. Gradually you do get used to the machine, and your body "learns" not to swallow the air.
Gas-ex and such are good after the fact, but do nothing to help with the sleep you've already lost. I use a chinstrap that I have to keep re-adjusting it, but it seems to help me.
Hang in there.