>Unfortunately, it's not just a boss I would have to re-record. It's a boss, a miniboss, and two very difficult passages where I narrowly avoid getting hurt (and both places I've had to rerecord 20+ times in order to just barely avoid getting hit)
Well, 20+ rerecords is not a lot at all. Seems like an easy tradeoff if the option is trying to hexedit it. But that's your choice.
>If I was to hex edit the movie, is there any way of telling exactly where the save state points?
Yes. Turn on the frame counter with full stop (.) , and load the savestate. Maybe you have to do it when the movie is playing, I can't remember if it's like that in Snes9x or not.
You can find all kind of keyboard shortcuts at
http://tasvideos.org/UsingEmulatorTools.html
But what you really want to know is not where your savestate is, but where the movie does the wrong thing, and try to fix that position.
You might also want to read
http://tasvideos.org/HexEditing.html
and
http://tasvideos.org/DesyncHelp.html
The FAQ is your friend.