My wife is an INFP, and she reports exactly the same experiences you are describing.
As far as erasing beliefs from Fi---
I'm not sure exactly what you mean by that, but if you'll allow me to take a guess, I'll put it this way:
You want to "separate the wheat from the chaff", so to speak---to decide which beliefs you want to keep and which ones you want to reject, right?
I've seen the effect that absorbing religious doctrine has had on my wife, and though some of it's good, some of it really ain't too pretty.
She hangs onto some beliefs that she isn't comfortable with, just in case they're right, but it constantly plagues her, and she feels an excessive amount of guilt.
It's probably scary to let some of it go, because it has been programmed, to some extent, into you by both fear-mongering and subtle suggestion.
I think the key is to decide which beliefs you really agree with, and which ones you're holding onto "just in case."
That may sound overly simple, but I empathize with you, and I don't mean to imply that it's easy.
But in the end, it does you no good to hang onto those "just in case"-type of beliefs.
First, determine which ones are your core beliefs, then slowly, at your own pace, take a close look at the other ones.
It may help to make lists, and to take some time to study multiple views on the particular beliefs that plague you.
I hope this helps, and I'll ask my wife if she has anything to suggest.
I feel for you, my Brotha.