I lost you here. Why?
Originally, you said:
Ultimately, the test of correctness is whether a holy work brings people to Christ.
So, I took your test of sound Christian teaching correctness to be that if it brought someone to Christ, then it was correct. Then you said:
If Jake and Jim met a man and each spoke to him, and Jake sent him to Christ then Jake spoke the truth, even though Jim might have succeeded in sending him to Satan.
I took this to mean that Jake was the true Christian. However, Jake failed to bring the man to Christ because Jim succeeded in sending him to satan. Therefore, Jake's true Christian teaching must have been incorrect because it failed to bring the man to Christ.
... because that is [what] Protestantism is all about: find out what you think the Bible said and find a church that fits you. If you can't, start your own.
I would respectfully disagree that Protestantism is all about coming up with one's own theology and then finding validation in one of a million different Protestant churches. I see that as an unfair stereotype. I know it wasn't true in my case. I chose my church because of its emphasis on following the Bible generally, not because of any pet belief that was relatively unique to that church. The only reason I am a Southern Baptist is because they were the first REALLY Bible believing church that I found. I could just as easily have wound up somewhere else, as long as the heart of the church was focused on God and the Bible.
For by grace you are saved through faith, and that not of yourselves, for it is the gift of God (Ephesians 2:8)
The above is quoted most effectively by Protestants as they defend the salvation by faith alone. (They also quote many other passages, but this is one where "saved" is not in the future tense; likewise Romans 8:24, 11:5, 1 Corinthinas 1:18, 15:2, Ephesians 2:5, Titus 3:5).
Well, is "are saved" referring to a completed event or continuing process? Likewise, is "Jake sent him to Christ" referring to a completed event or continuing process? The quotes alone do not say (checking with the original Greek of the Epistles, "este sesosmenoi" is no help, as the same dilemma exists in Greek). We need to look elsewhere for the answer, and we find it:
But he that shall persevere to the end, he shall be saved. (Matthew 24:13)
Likewise, Matthew 10:22, Mark 13:13, and dosens others where "save" is also in the future tense or conditional mood, point to salvation being a lifelong process. That view is also consistent with multiple excoriations to do works of charity for the sake of the salvation (most explicitly in Matthew 25, Phillipians 2:12).
Going back to Jake, my meaning becomes clearer if we observe that it is possible to be sending one to Christ without the poor devil arriving there. Still, Jake spoke the truth, did he not?
I would respectfully disagree that Protestantism is all about coming up with one's own theology and then finding validation in one of a million different Protestant churches.
It is less true of the Baptists than of doctrinaire Protestants, I admit. This is why I like them; after all my own wife is a Baptist. Of course most Protestants of every description today simply go to church they know and love in a positive experience of Christian faith, and could care less about protesting anything or developing their own doctrine. Still historically, all branches of Protestantism developed as I describe: someone reads the Bible, feels dissatisfied with the religious practice he finds around him, protests them, convinces others, and voila, a new denomination is born. Also, when one discovers religion as an adult and seeks to join a church, the Protestant denominations would all, typically, try to convince him by describing their doctrine, when the Orthodox or the Catholic would say simply, this is the Church Christ founded, come and we'll tell you what you need to know in the fullness of time. No marketplace of ideas where I come from.