You might like to give this a slow, careful, and serious read:
http://www.scborromeo.org/papers/solafide.pdf
I am not Catholic.
I have many Catholic family including Priests and Nuns, that is the limit of my Catholic experience.
I do know that Catholicism was NOT the only Christian Church around, Catholicism was the predominate group, which controlled many governments.
I was curious what the current Pope had to say about Luther, which is why I included the quote.
I will read your pdf, soon but not tonight, I’ll let you know what I think.