1. Okay, I'll try that. Thanks for the tip!
3. I'll do some testings here.
4. Must test it first, which is more difficult than I thought. They always slip on the ice (they need better boots).
5. Very motivating

I just noticed that unmovable items are the reason why characters get stuck in their reaction sometimes. The engine doesn't ignore CharacterMoveItem for unmovable objects and also doesn't interrupt the reaction. The only way to make the character react again is to interrupt the reaction manually or by certain actions (like requesting dialog, or by other reactions). That's not good... It's definitely necessary to exclude all of these items. A check for 'CanBeMoved' or 'CharacterCanMoveItem' (also checking required strength and telekinesis) would be very helpful.
Edit: Maybe I can work with ItemIsMoving. Actually the better idea...
Edit2: Even better: just setting an integer after CharacterMoveItem and checking it on a timer. If it isn't set it will interrupt the reaction.