Adult male, s/p bilateral cleft lip & palate

My adult son, now 35, is a very healthy male born with complete bilateral cleft of lip & palate. He is having MAJOR problems especially sleeping due to regularly waking up 3-5 times nightly due to dry mouth & feeling as though there is a heaviness on his chest. He works, does not engage in drugs or excessive alcohol and regularly works out. He has been seen by more doctors than I care to recall. Anyone have any suggestions on who might help? CAN fall asleep WITH Ambien, but not successfull in sleeping more than 1-2 hours at a time, Desperate! Does have health insurance.