The Gate is narrow.
I see the root of his problem.
>>and an intellectual view of the Christian faith and my Christian duty<<
Intellectual view? I can find no scripture that extols the ascent of the intellect. I can't find the verse that says "with the intellect a man believeth unto righteousness". What I do find is this.
Romans 10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
And this.
1 Corinthians 1:19 For it is written: "I will destroy the wisdom of the wise; the intelligence of the intelligent I will frustrate."
>>Augustine taught that we literally merit eternal life when our lives are transformed by grace.<<
There it is! That carnal human desire to "deserve" or "merit". Not relying solely on God but the carnal sinful desire to "be somebody"!
>>The Church was both the authority on Christian doctrine as well as the instrument of salvation.<<
The "church" is the authority and instrument of salvation? No it's not. God's word is the instrument of salvation.
Romans 10:17 So then faith cometh by hearing, and hearing by the word of God.
Believers aren't "born of a church" or "by a church".
1 Peter 1:23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
It's not some "church" that guides us nor is it some "theologian".
John 16:13 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.
This poor man was deceived from the beginning. His "idols" by his own admission were men not Christ. He put his faith in men and institutions not Christ. He listened to men not the the indwelling of the Holy Spirit. Still today he looks to the "church" for salvation not Jesus Christ.