Welcome to the "Bionic Butt-Club"
What is your original pain condition if I may ask?
Insurance companies can play some tricky games. Even if you do wait till the next year and change insurance, you could possibly get denied as "pre-existing condition".
The most important part of the 'Red Tape' is getting the doctor to send your insurance a letter of 'medical necessity'.... and then once approved, get it in writing. I'm not sure regarding the Medicare "DME" issue.....Medicare has made so many changes lately that I would talk directly to a Medicare Rep (and get THAT in writing

)
And yes, you made a good judgement call regarding the cost in the longrun....(Even if you DO have to make pymts up to $5K, assuming your SCS proves successful) My pain meds were running me almost $1k a MONTH.
Like you, i spent 100's of hours online reading up on this procedure and even at that, when it came down to the nitty gritty, a few 'surprises' were pulled on me (such as battery placement....and in another's case they completely changed the manufacturer without his knowledge/consent......you know who you are M56PJ

) Nothing to fret about, just saying, be open to variables.
All your Q's are good ones, these things are important for us to have 'peace' with......somehow it all ends up working out. Sponge baths, plenty of powder......you'll get thru it. Just read thru alot of the threads and posts here and it'll paint a pretty clear picture. Listen to your body.
It's good to have you on board!
Stick around so we can learn from YOU as well!
It's a TEAM effort, no doubt about that!
Rae