A data table that isn't painful

Here's my table: <paste>

Fix the things that make tables unpleasant:
- Horizontal scroll inside the table's own container, so the page
  never scrolls sideways.
- Real table markup with headers — not divs. Screen readers need the
  structure.
- Sortable columns that announce their state, and are operable by
  keyboard.
- A sensible answer for phones: which columns matter, and what
  happens to the rest.
- Sticky header if the table is long.
- An empty state, and a loading state that doesn't collapse the
  layout.

Tell me which columns I could drop entirely — most tables show more
than anyone reads.