Update: We're still in the NICU but Jack is under oxygen and doing well. All anatomical and blood abnormalities have been ruled out - so we're very relieved to know that. They say he just needs time for his lungs to open up. I haven't heard an official diagnosis, but it looks like most of the real scary options have been eliminated.
We know these things for certain: Whatever happens, God's grace is enough AND He got cuter overnight.