I am confused as to why Quirrell/Voldemort would leave behind the false clue of the animagi potion. Revealing an escape mechanism that may prove usefull later doesn't make sense.

So now Amelia Bones changed the rules of visitation at Azkaban to prevent forming a new animagus. However, the prison is still vulnerable to an unregistered Animagus from escaping (unless they have detection methods?). Escape like this would still lead to a Sirius style manhunt unless a realistic corpse was left behind.

Interestingly, Sirius whom in this fiction is probably already escaped (how he did it un-noticed is beyond me) may have free run of Hogwarts. Per cannon, Pettigrew in animus form was not warded from Hogwarts proper. I wonder if Sirius's presence within the castle was the glitch Fred and George noted on the Marauder's Map in chapter 25. They noted two glitches, one intermittent and one permanent. Pettigrew's whereabouts if still indeterminant as well since he didn't hid in plain sight as Scabber in this fiction (perhaps his death wasn't faked this time).