I have had just about the same sleep study results and the same CPAP therapy results that you have had over the last 8 months. I don't want to scare you but I am now headed for stints or by-pass surgery next week, I'll know once they get in there and look. My sleep apnea has gone undiagnosed for 30 years and my 20 year average BP was 240/120 with medication being useless. Since May of last year my BP has been on a rollercoaster, but in the last two weeks it has flattened out to 120/80 and lower the day after I was prescribed a blood thinner. I was just prescribed Eliquis (blood thinner) due to A-Fib. This is the first time in 30 years my BP has been normal, so don't give up hope and continue to think outside the box with you health care professionals. The Eliquis was prescribed so they can get ready to cardiovert me after the heart plumbing is complete. I just hope you are young enough to get past this and have a good life.
Stay with the CPAP, it's a wonderful thing for those that need it.