Wow, Charles —
I was exactly in your friend's position when I was a sophomore in college and I worked my way (by God's grace) back into the Catholic Church.
Let me recommend several things.
One, share with him the book Catholic and Christian by Dr. Alan Schreck. This was one of the things that sparked my way back — first of all it was very irenic (i.e. the opposite of polemical) and explained Catholic teachings in terms I could understand as someone steeped in Evangelicalism. The main thing that sparked my interest in it was his description of what the early Christians believed — the testimony of the early church Fathers.
That's the second thing I recommend that he study — the testimony outside of Scripture of what the early first through third century Christians believed. Obviously it's not inspired and infallible material but it provides an interpretation and a context to Scripture.
How did the early Christians interpret such texts as John 3:5?
(Hint: being born again was baptism, not having an emotional experience or giving your life to Christ for the first time.)
The third thing I'd recommend is putting him into contact with Catholics who really believe and really live the faith — he already has that in you. Without a community to shine the light of Christ, hope is dim. I can recommend a ton of other books but I don't want to overwhelm. Conversion stories may help — check out the three Surprised by Truth books by Patrick Madrid. Or, Born Fundamentalist, Born Again Catholic by David Currie. Books by Steve Ray are good too.
For you, I recommend Catholicism and Fundamentalism by Karl Keating. Use your discretion about whether to pass it on to him; it's a bit snarky and may turn some people off.
The one issue I could never resolve during my Evangelical detour as I called it, was how I could rely on the Bible without someone infallible to tell me it was infallible and what was in it?
The Bible didn't just fall out of the sky (a la Islam). Some books were disputed for many years. Revelation was so disputed that it isn't even read in churches in a major portion of Christendom (I refer to the Eastern Orthodox churches). In some places for a while, the Shepherd of Hermas was accepted as canonical scripture, or First Clement to the Romans. The first extant canon of the New Testament is the Festal Letter #39 of St. Athanasius in 367 A.D.
- So what did Christians do for over 300 years after Jesus ascended when they didn't even have a solid canon they agreed on?
How could I trust, as infallible, a bible that wasn't even settled until a time when all these pagan accretions (so I thought) and objectionable doctrines had crept into Christianity?
It was a contradiction: The very same Church I had assumed was corrupt by that time, drew up the canon of infallible Scripture, possibly judging it by those corrupt doctrines. Add this on top of the fact that, Bibles (and books in general) were hand-written and were only obtainable at astronomical cost and, for that reason, literacy rates were abysmal. The approach that Evangelicals take today just was not envisioned by the early Christians. This is not to say that Scripture is not inspired and inerrant, nor to say it is not profitable to study it, just that the early Christians had a more corporate approach to doctrine:
Scripture was read and interpreted in the context of a community, not every man for himself.
What finally put the nail in the coffin for me was encountering a bewildering array of Christians, all of whom were sincerely convinced that the Holy Spirit revealed to them the right doctrine from Scripture alone but they all disagreed on that doctrine. I had my own definition of orthodoxy and I kept having to pare it down to accommodate groups that were sincere and didn't appear to be cults but differed in their interpretation. The final straw was people who claimed Baptism was purely a cultural artifact and wasn't part and parcel of the Christian faith.
Anyway, I am starting to ramble. That said, be patient with him and pray for him. As Amy Grant says, It takes a little time sometime, to turn the Titanic around . . . It's an investment of time and love. Plant seeds. Someone else may water and someone else may harvest. I think I genuinely had to go through my detour to learn what I needed to know.
Don't judge and be gentle, but firm.
May God bless both your journeys!