Figures, 30 seconds after I type all of that I figure how the On Screen Keyboard is supposed to work.
At least for me I had to enable the keyboard while in Tablet Mode and then I got a bunch of other options, including the size and layout of the keyboard as well as a "launch when needed" option. I swear, sometimes these things hide themselves from me just so I'll get frustrated.
I still looking for how to change the scrolling in FF though.
Black screen with cursor can be bypassed by pressing ctrl+alt+del, at least on my HP laptop with Mint and KDE Plasma 5.