I was able to get the trackpad fully functioning by using the 2 articles below. After adding sys-usb dom0 allow to qubes.InputTablet, the solution required installing libinput-utils in dom0, then creating 2 files in dom0:
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/etc/X11/xorg.conf.d/30-touchpad.conf
libinput - ArchWiki -
/etc/libinput/local-overrides.quirks
Debugging touchpad pressure/size ranges — libinput 1.22.0 documentation
In local-overrides.quirks, I set AttrPressureRange=2:1.