I had an issue with teeth shifting because I wore a FF mask very tight around the chin and slept on my side. It does happen. But a nasal mask shouldn't be causing that. Dry mouth can be a problem--are you having that issue? The most common cause of teeth shifting is bone loss from osteoporosis. Do you have other signs of that? I take a vitamin D3/K2 supplement that's supposed to prevent this.
It is not a reason to stop CPAP. You need to find a better mask.
With respect to not seeing much improvement in your health issues with your CPAP, that's another matter. Is your treatment optimal? We might be able to help you determine that if you are computer savvy enough to download Sleepyhead, a free software program, and post your data. Often doctors will leave your settings at "good enough" rather than delve into the data to see if it's truly optimized for you. The fact that your symptoms aren't much better raises the suspicion that there's room for improvement.
Meanwhile, "virtually eliminating [your] sleep apnea" is no small thing. How much worse would your health be without CPAP? Nobody knows the answer, but no doubt you might have other medical issues without it.