With both xf86-input-evdev and xf86-input-libinput installed, the keyboard and touchpad both work fine. Dell Inspiron Touch Pad not Working (Windows 10 32 BIT) - Dell Community.
UPDATE!: Was able to fix this by uninstalling the dell touchpad drivers and using the previous Inspiron 3542 touchpad driver. A friend I work with asked me to check out this laptop that belongs to her daughter. I did all the same procedures you tried with the same out comes. I got back my vertical scroll bar (which had been lacking) and also the Dell Touchpad icon in bottom tray (also wasn't installed on this laptop).
