Hmmm...

For me, the stem always comes loose as soon as I tap the tapered nut free.

It looks like you have it pretty well stripped down. You could probably simply remove the handlebars to ship your bike, but reassembly will be a pain if you have to remove the bars each time.

I'd go ahead and remove the brake, then clamp a pair of 2x4's around the fork crown, and see if you can work the stem loose. Perhaps remove the bars, and clamp another pair of 2x4's around the stem, although get too much leverage, and something is bound to break.