What a horror show. My MM Homoeomma chilensis attempted a post ultimate moult. I put him in the fridge until he stopped moving, about 20 minutes, and then into the freezer to kill him. I hope I don't experience this again.
It's a reality that all of us might have to face at one point, if we have any males. Stuck moults absolutely suck - especially when there is no chance that they will make it.
Even when there might be a chance of saving a tarantula in a stuck moult, the chance that a MM makes it out alive is extremely low.
I did the most humane thing I could do for him.