Battle replay, fast forward / backward + stop ?

[Taqwus]

You can switch to a faster speed (faster projectile/missile use, for instance) using 'f'; you can step through one turn at a time as well by another hotkey ('n' if memory serves; I'm on a different machine in a different house at the time being). You can immediately end it by hitting escape.

You can't actually go backwards, as far as I know.

[Tichy]

It's not escape that quits battle replays. It's "q". Esc quits every other screen in the game. Odd, yes.

[Wick]

Ending it uses q, not Esc.