As is customary in these sorts of things, mere minutes after posting this I figured out what I was doing wrong. For anyone else who gets stuck like I did, as much as i doubt there will be anyone, the pixel value is being divided by the maximum height in the lines
function evaluatePixel(sample) {
return [sample.DEM/1000]
}
meaning that in order to get an absolute altitude above sea level for anywhere in the world you simply change it to
function evaluatePixel(sample) {
return [sample.DEM/9000]
}
However this still presents a problem of resolution, since every brightness value for a pixel is roughly equivalent to 35m from the previous value which is less than ideal.