Problem solved. It was insanely difficult but...
I used the offical uninstall tool to force a reboot into safemode.
The comptuer crashed several times with "Your PC has encounted a problem and needs to reboot
"
Did a small system resotre and fixed startup errors.
PC booted into Safemode and the keyboard worked.
Though because of the system restore the official and unoffical 1.3 removal tool were nowhere to be found.
Downloaded them both on my Galaxy S 4, though I couldn't transfer them to the computer in safemode (drivers hadn't been loaded)
So I forced USB mass-storage mode with a Root app, moved the removal tools to the ExternalSD and copied them to the computer.
Ran the offical removal tool. Rebooted when it was done.
Ran the unoffical removal tool to clean up the last of the bad install.
Disabled Windows defender from the control panel.
Installed the ONLINE INSTALLER (4mb) and chose custom settings, but allowed everything. Inserted license file etc.
Bam, it executed no problem without any issues. (Previously had the persistent 'You are unprotected!" error, in addition to no working keyboard) when using the OFFLINE installer.
Seems to be working now.
Dunno if disabling Windows Defender helped, or if it was using the 4MB Online Installer, or both.
Finally I get to use what I paid for.
Took 20+ reboots and a whole night of messing me around but whatever.