In the heat of battle, is hit point loss a wound?

[pemerton]

there's no rolling needed in AD&D because a fighter can kill a number of level 0 characters up to their level?

In AD&D that rule permits attacks, but not auto-kills: the attack dice still have to be rolled (though, especially with specialisation, minimum damage is likely to be 4+, which will be fatal for many targets of fewer than 1 HD).