Nice start there. Looking forward to how this progresses.

Ralf's uploaded a signed version now, that should take care of the warnings.

The easiest way to use textures (fill styles) from another style is to first make a blank dummy map in the style containing those textures, then in your actual map, go to Draw -> Insert file and pick your dummy map and hit ok. Once you return to your map with the dummy map on your cursor ready to place, just hit escape immediately to stop placing it.

Horrible manager office, no window....

Yes, just hold down the control key and click on an entity to deselect it.