It is not that the Bible cannot be trusted. An atheist with no plan or desire to serve God can read the Bible and get nothing from it except what he wishes to and expects to find. You receive something good from the Bible, because you already know God. You do receive direction from the Holy Spirit in your reading or studying. I do also as does any believer who opens the Bible and reads it.
Why do we come up with discrepancies or even seeming contradictions among believers?
We do have different beliefs from one another already. Those beliefs and our overall level in our walk with God do affect how the Holy Spirit opens us up or even may limit the Holy Spirit because some things that we have already decided are right... whether they are or not. Everyone who is serving God at all can grow. Whether they do or not is not up to God. It is up to the individual. Our choices in what we will even consider make a difference is what He will show us.
Remember what Jesus said?
"Verily I say unto you, Whosoever shall not receive the kingdom of God as a little child shall in no wise enter therein." Luke 18:17
Now recall your own childhood or what you have observed more recently in young children you have known. What do you suppose Jesus meant when it was applied to a physical adult? Children have few if any habits when they are very young. They develop habits as they grow, both good one and bad ones.
I would think that Jesus wants us to come with no preconceived habits or ideas in order to for the Holy Spirit to impress on us from God's store. He won't impress anything evil on us, but we, because of implanted habits, ideas, beliefs, etc. limit access yo God Himself. Do we really trust Him? If so then why would we worry about even considering an idea or doctrine or belief that we had already rejected previously? God can take care of Himself... and if we will allow it, He can take of us as well.
What men call "freewill" is simply choosing God's Way or some other way. When we choose some other way, even a way that seems good to us, do we not block the free access of God to our heart?
"There is a way which seemeth right unto a man, but the end thereof are the ways of death." Prov 14:12
Would you have already take a way that was leading to death because it seemed right to you at the time? Perhaps not, but that is only perhaps. Who but God knows.
Reading the writings of the early church fathers or more recent theologians is not an evil thing. We might learn some very good things from them. But, don't decide to go along a particular road just because some man, even a very good man, did. Your road is not theirs and theirs is not yours.
While there is only one highway of holiness, the work necessary as we travel the road does depend on what God requires of us as our function as a single individual part of the Body of Christ. We are not all the same. God does have different things in mind for each of us. Basing your conclusion on someone else's conclusion may lead you off the road because you were not also listening to God as you considered that other person's conclusion.
Remember Hosea versus the Apostle Paul! They were both men of God.