Hmm, why not make chaos floors push entities up slightly ?
Combat around an exit makes using direction keys a liability. This has been mentioned before and I have foreseen all the consequences - they would be bad and result in ever more complicated hacks to avoid anything interesting ever happening at a stairway or portal. Not happening. Sorry.
With this in mind I'm curious why you made open chests and pick up items the up arrow key ? I've run into quite a few items/chests at the bottom of stairs.