I don't really post here but seeing as I'm actually a sleep scientist, I thought I could offer some help/advice.
I'm sorry about your diagnosis. Having said that, it's great that it has been identified early and you're getting on to treatment. Your RDI and Sats are not that alarming. You will however, notice a huge difference in your day to day health and energy levels if you stick with it.
Has the doctor suggested to maybe wear it during the week and have weekends off? I work in a children's sleep clinic, so CPAP compliance can be tricky in the little ones and sometimes that kind of compromise is enough.
The blood tests will be for thyroid function, iron etc, nothing to worry about. It's not a routine part of the sleep study, but it is very common for doctors to request it (to see if anything else is contributing, like anaemia).
The oral appliances are used in certain cases where the sleep apnoea is attributed in part to facial/jaw anatomy. The MAS for example (Mandibular advancement splint) is used mainly in patients with a retracted jaw or with mild to moderate sleep apnoea, like you, so it's worth talking to your sleep doctor to see if you'd be a good candidate for it. There might be a reason the doctor won't be too keen to prescribe that and it could be due to your facial anatomy. There's a good chance it might not work.
Unfortunately, the god standard is CPAP. It works every time, on everyone. It is life-changing.
As a bonus? It was invented right here in Australia!
I hope you give it a try and I hope it changes your life.