....”I’ve been assured by a few FR Roman Catholics that God will strike down a heretical Pope.”.....
If that were actually true than how would they account for the broad range of popes in their history who certainly were that and a whole lot more, who seemed to fair well over a long period of time?
Don't be pointing out the sandy soil of the RCC foundation. They are The One True Church according to . . . . well just take their word for it.
It appears to me that the approach is to look back and pretty up the historical timeline by declaring this or that particularly bloody or nutty individual to be an anti-Pope. Hindsight is 20/20.