I see that you wrote your post in November.  I hope you had your air pressure levels adjusted by now.  Absolutely, with a weight loss of 75 lbs, your pressure needs will change (likely drop).  If your machine doesn't monitor you each month adjust itself, please have a professional adjust it.  It likely has an SD card in it (or some memory card of some sort).  They can look at the readings for it and adjust it to what you need.  Having too little pressure will have you waking up because you're not breathing.  Having too much pressure can cause problems with the heart for example, especially if there are problems like congestive heart failure (not saying that's your case).  Best of luck.

If you have sleep apnea you probably snore somewhat...

The first appointment they just ask you questions. I was refered to a pulmonologist because my ABG showed it was lower than it should be. The surgeon wanted to know if it was sleep apnea or the extra weight that caused it. The pulmonologist recomended a at home sleep study. I picked up my equipment(they showed me how to uses it)  and slept with it for 2 nights(at home) then returned it.  My next step is meeting with the pulmonologist for results. They said i will only need a C-pap if i am in the moderate/severe range. 

It depends on the clinic and program. My program requires everyone to at least have a home sleep test because over 70% of people with a BMI > 35 have sleep apnea.

They have a new device you can get surgically implanted in an outpatient procedure. It is not being done near me, but maybe it is around you. Here is the website. https://www.inspiresleep.com/