I agree that on issues that are not clear and have not been defined, there is room for discussion and debate.
It is good to see that you are at least backing away from your previous post where you made no distinction. All you said was that if God revealed it everyone should believe it and it is all essential. This reminds me of what Augustine says, “In essential unity, non-essentials charity, in all things love”. That is no different then what I’m saying.
Furthermore, in your above quote you beg to many important questions for it to be of any value or workable. For example, who determines what is clear? The clearness of a teaching is not a sign of it being essential. There are many things the Scripture teach with clarity, but no one should make them essential to the Christian faith. Also in most cases we are beyond “discussion and debate”, because both sides agree to disagree.
Since we’re on Sola Scriptura, where in the Bible is this distinction between “essential” and “nonessential” doctrines?
The essential things are those that the Scripture speak of as necessary for salvation and those things that derived by good and necessary consequence from Scripture. For example, the Scripture never explicitly say one must believe in the Trinity to be saved, however it logically follows if you don’t believe in the right God then you cannot be saved.
Who has the authority to determine what is within the “pale of orthdodoxy” and what is not?
Ultimately the Scriptures are the final authority, but they must be interpreted to arrive at this truth. Who interprets the Scriptures? Anyone can, but each church should setup elders as the Scriptures teaches who have authority in the church.
What about Pentecostals who believe Jesus is God, but don’t believe in the Trinity. They says that Father, Son, and Holy Spirit are all titles and modes of one person within the Godhead. Are they okay?
No, they are not okay, because that is an essential. If you don’t have the right God then you can’t be saved. Otherwise I could believe that Jesus was not even human or God.
I hope you know that there are also Protestant churches who believe in the necessity of baptism for salvation and in baptismal regeneration (Lutheran). That deals with salvation, the core of the Gospel.
Lutherans affirm justification is by faith alone, believing this happens at baptism is not a denial to me of the Gospel. It is a difference in when the application takes place.