Just read all this and... my God how terrible!!! So sorry you both are going through this! I'm sure you're doing everything you can right now. I'd be on the phone with the police, any neighborhood help lines, city council, solicitor, any group or organization with the power to intervene! Your demented neighbors are clearly becoming more aggressive the more you try to protect yourselves and the police need to do something about this, more than just 'talking' to them.
Wonder if you can both leave the flat and be sure they see you leave, then one of you sneak back in a window and wait for them to break in. Catch them on video. Ugh, how sick these people are!!