But actually, religi/on/o doesn't make any sense. That would have to be a fraction of a whole divided into religion things ... which doesn't make any sense as religion is not a number. A portion of religion would have to be religiero.
-on- / -op- (fraction / group of something undefined, specifying a division or multiplication of the root)
-er- / -ar- (part / group of something which defined by the root, not identifying how many)
triono = a third
triopo = a threesome/trio
triaro = a group of threes (we don't know how many threes, but the group consists of threes)
triero = a particle of three ... whatever that would mean.
I suppose it could also be a "religion-one" (as in acetone) or a "religion-on" (as in neuron, nephron) - PIV says that "on" can mean not only the "fraction" but also a kind of ketone or an individual part of certain biomolecules, organs, or tissue.
So maybe you consider your religion to be like a kidney, then an individual component of it could be a religion-on, "religi/on/o", with meaning 3?
Faith is - fido. Well, mostly. The word "faith" (in English) seems to mean something different to each person. I would go so far as to say that "he lost his faith" is a valid translation. Whether it's a better one, I'll leave to other people to fuss about.
(To be clear - nothing wrong with fussing. I just don't feel like fussing now. Grin.)