This is the heart of the matter and it's where Fr. Corapi is making a great mistake.
Those are not the only two choices. In particular, option 1 is a false option. "Quietly lie down and die"?? I presume the word "die" is Father's take on waiting patiently for whatever ecclesiastical processes are currently underway to run their course and to submit to their outcome. It's clear from the rest of his letter that he believes these processes to be flawed and that he will not get a fair hearing.
Herein lies his essential problem. It is a crisis of faith. He does not believe that God is in charge and that, as St. Paul says in Romans, ....."all things work to the good for those who love the Lord". He's lost faith that God can work through the weak and perhaps corrupt humans in whose hands he now finds himself.
As a result, he has decided to take matters into the hands which he believes he can trust; his own.
I'm making no statement as to the truth of the original allegations. Just his decision to (apparently) abandon the priesthood.
“Herein lies his essential problem. It is a crisis of faith. He does not believe that God is in charge”
On the other hand, maybe he does think God is in charge and he is supposed to go another route.