How do I increase mouse pointer speed past the limit?

Found a pointing nipple user /s

Set the physical mouse to a higher dpi? Probably not what you’re asking though.

Can you type something in the number field next to the slider?

If the maximum speed pointer is too slow (which can also be subjective) for your touchpad, this might a be driver bug or some missing calibration for your variant of hardware. Reach out to libinput devs, they track issues here: https://gitlab.freedesktop.org/libinput/libinput/-/issues

For me putting the slider to 1.0 makes the touchpad so fast it’s barely usable