First, here is a hug from the show me state (MO). We have been where you are and hope to never be there again. Talk to the Hospital. Some will not even proceed without insurance approval, some will provided you are willing to sign on the dotted line...
Second, if you do not have a job currently or are underemployed, take the new job. You have nothing to lose and your boss may be very sympathetic to your situation.
Third, have you talked to your doctor about a possible steroid taper? That worked miracles in my son and bought us enough time until we could get IVIG.
Fourth, I think insurance companies are part of the "evil empire". They are a necessary evil, but I despise them just the same. On the plus side, if you end up having to pay out of pocket, it greatly reduces your taxable income. This is sick humor, but happened to us three separate years.
Lastly, have you tried an insurance advocate? We used one and I highly recommend them. PM me for the name.
Know that there are other mom's in your corner. We are here to support you.