I had significant sleep apnoea when I was >180 lb together with constant neck and back pain, so much so that I thought I was suffering from fibromyalgia rheumatica. I have largely recovered - CPAP is no longer mandatory to eliminate day time somnolence.
You are 156lb at 5'11, I am 5'5 at 152lb, therefore my BMI is greater than yours. Since you are a mere 29 yr old, you should be able to manage far more exercise than me at age 61 yr.
I speak from personal experience, and not as a physician (although I am one), on what I think is best for you, provided you have no predisposing factors that may prevent you from exercising or other physical disability. Presumably your doctor has cleared you of serious spinal disease such as cancerous deposits on the neck bones!
1. Weight-wise, you are Okay. No specific action on this front.
2. Intolerance to CPAP is a well recognised problem of this otherwise superb therapy involving no drugs. This is a personal preference which is probably exacerbated when you have so much pain from this, that or the other. Your persistent pain issue can not and should not be overcome by long term night sedation, risking later substance abuse.
I would suggest at least one hour of eliptical cycle training daily to train all 4 limbs with no impact on the joints, and only start purposeful stretching of the neck and back half way through the exerise session after your muscles have warmed up. The exercise machine does not need to add resistance for the initial few weeks. Don't waste your money on passive massages - be active and stay consistant at your exercise regime.
Splint your neck with a cervical spine (neck) support that fixes your head in a steady position to prevent bending the neck forwards (up when you are lying down). This support, comes in a few different sizes, is basically like a vicar's dog collar that rings around the neck but it is taller in that it is around 6 inches high. Note that if it is comfortable when you first put it on, it is too small to adequately stablise your head and neck. It must be stiff, and minimise head and neck movement throughout sleep.
Abandon what ever pillow you have and sleep on a firm, orthopaedic mattress.
Take sufficient analgesics for the first 10 days, together with adequate muscle relaxant before bed. Note muscle relaxants are nearly all addictive tranquillisers, therefore your doctor should limit your use of these "relaxants".
If you have significant day time somnolence which may cause you danger, e.g. falling asleep at the wheel whilst dring, then you might be better off to continue the CPAP machine for now.
It is entirely possible that you may resolve your present perdicament before Easter. I would be delighted to hear how you got on in a couple of months' time. The collar may be a little hot in the summer, therefore you should try this regime out over the current winter of the Northern Hemisphere.