Hello @Eyetoother, thank you for the post 
Sorry to hear you’re having troubles with the app and sorry you’ve had to go through all the troubles with installing/uninstalling so many things on your computer because of this 
It seems like this one specific behaviour has already been identified in the past by another user of this forum:
The most likely cause is adding system fonts into FontBase, then activating/deactivating them, while they are already activated by the OS. This can get the operating system, Windows in this case, confused by having two exact fonts active at the same time. We do not recommend adding system fonts into FontBase and activating/deactivating them. System fonts are always active, by their very nature.
I believe the cause and the solution for this are also discussed here Crashing Search bar, app store and apps and they should fix the issue you’re experiencing.
Hope this helps,
Yuriy
FontBase Dev Team