RE: I think I'm going to quit my job soon.

Right, I read your post and all the comments and I think it would be a wise decision to make.
Unless it's going to give you heaps of stress to not have a 'fiat' income coming, then I'd definitely do it.

I have enough money to live on for years at this point even without the blog rewards.

_{Taken from a comment}
This right here. If this is your situation, then I'd say, what are you waiting for!?
I can understand that waiting to be 'paid' off by Amazon could be a good thing but if it is causing you misery and headache, I'd say why not just stop now?
To let go of something we have become used to doing on the regular can be a scary thing but judging from your post and comments, I'd say you're good to go.
Be free of the restraints of Amazon!

^{Just my two cents!}