Unlike you, I don’t subscribe to Sola Scriptura, so I don’t have the same logical problem.
So I reiterate: you claim Sola Scriptura, as do Lutherans, Baptists, Evangelicals, Calvinists, and Fundamentalists, among other Protestant denominations. Yet we have mutually exclusive theological positions that emerge, as I have already pointed out.
Who decides who is right? How do you determine which one is true?
Good questions!
God decides which one is correct.
We are to test each doctrine by comparing it to what God has revealed to us in His Word. (2 Tim.3:16,17). Man is not to add to or subtract from His Word. This is repeated three times in the Bible. In the beginning (Deut. 4:2), in the middle (Prov. 30:5,6 and at the end (Rev. 22:18,19).
No, you have a much larger fundamental problem. Remember, the first step in solving your problem is first recognizing you have one.