Fun premise that feels like something I’d read in an early module or inspiration. The “body count” is equal parts hilarious and a helpful tracker.
The portal racetrack is also pretty neat, but I wonder whether you might need to further adjust the encounter checks there? It should only take the Ogres about 5-6 turns/minutes to run the loop, and maybe an extra 1-2 as they debate who won. So it’d be pretty tough for a 12” speed PC to NOT see it. Maybe reverse the odds to 5-in-6, then lower one step each time you do encounter one?