I saw your question yesterday on reddit as well.

When I tried to use threads in python and gtk, it took me like one night to figure it out.

In the end it was as simple as

GObject.threads_init()

Gdk.threads_init()

in the beginning and then spawn threads like you normally would in python with something like

watch_thread = Thread(target=self.function)

watch_thread.daemon = True

watch_thread.start()

I have no idea if that helps you. But I do hope so. I will also take a look at your code and might edit my answer afterwards :)