The bark on most of the tree has now turned black. I believe my little man has died.

I'm sorry. Bark turning black is not a good sign.

It may have had a root rot. Even with good drainage sometimes they need to be sheltered from continual rain. I have to put mine under eaves in the winter otherwise they'd be rained on nonstop for months. The best drainage in the world can't make up for continually wet soil.

Did you have the pot raised up off the surface so the drain holes were not sitting directly on the surface? sometimes they plug up and can't drain even with screening. If the pot has feet that's usually enough.