It's been implied it wasn't actually him. Alanis is usually cagey about it (the same way Carly Simon is about "You're So Vain"), but she's also straight up denied it was him a few times.
Dave himself is the one who mainly says it was him, but he's also changed his mind a few times and denied it as well. And there's like 3-4 other guys who apparently fit the bill.
The moral of the story is apparently Alanis went down on a
lot
of guys in theaters.
The most likely theory is that it's a song based on multiple relationships combined, and not one specific person.
Far-Queue posted...
cut it out
https://youtu.be/BBBCwpYp0mg?t=26