ServerName fix confirmed good. That port-80 output shows a full set of httpd worker processes (2613, 2616, 2658–2660, 3177–3184) still alive and bound — the "Stopping httpd: [ OK ]" from the restart was a lie, or at least incomplete; the old instance never actually went down, so the new one couldn't bind. This is a stuck/orphaned Apache process group, not a config problem.
Kill the whole set cleanly and restart fresh:
killall httpd
sleep 3
ss -tlnp | grep ':80 '