This is the greater issue, in my opinion.
The main strike against Sola Scriptura (ss), in my view, is the belief that everyone can come to the truth by just reading the scriptures. If you recall, ss arose out of the Protestant Reformation in the 1500's that ultimately rejected the authority of the Roman Catholic Church. Further on, pressure from the Age of Reason (17th century) cemented education and higher learning as the standards of man's progression. Advanced degrees and study, above most other qualities, qualified people for leadership, even leadership within the church.
The Bible actually says that a certain person has all authority in heaven and on earth (the Lord) and that that person has charged His unique delegate, the Holy Spirit, as the One who dispenses that grace to men. The pattern seen in scripture is the Lord multiplying Himself within others by the dispensation of grace and then that grace, so given, being dispensed from carriers of grace to others. Jesus had the Twelve; Paul had Titus, Timothy and others; Peter had others; John had others; etc. By this progression the Lord built the House of God in scripture. He is still building this way. Few receive it.
Yes, and IMO unification will occur to the extent Christians believe Sola Credo/the Gospel, which can be elaborated as:
1. There is a/one all-loving and just Lord or God (Deut. 6:4, John 3:16, 2Thes. 1:6), who is both able (2Tim. 1:12) and willing (1Tim. 2:3-4, Ezek. 33:11) to provide all morally accountable human beings salvation or heaven—a wonderful life full of love, joy and peace forever.
2. Human beings are selfish or sinful (Rom. 3:23, 2Tim. 3:2-4, Col. 3:5), miserable (Gal. 5:19-21), and hopeless (Eph. 2:12) or hell-bound at the judgment (Matt. 23:33 & 25:46) when they reject God’s salvation (John 3:18, Rom. 2:5-11).
3. Jesus is God’s Messiah/Christ and incarnate Son, the way that God has chosen (John 3:16, Acts 16:30-31, Phil. 2:9-11) of providing salvation by means of his atoning death on the cross for the payment of the penalty for the sins of humanity (Rom. 3:22-25 & 5:9-11), followed by his resurrection to reign in heaven (1Cor. 15:14-28).
4. Thus, every person who hears the NT Gospel needs to repent and accept God’s justification in Jesus as Christ/Messiah the Lord or Supreme Commander (Luke 2:11, John 14:6, Acts 16:31), which means trying to obey (Phil. 3:12, 1John 1:8) His commandment to love one another (Matt. 22:37-40, John 13:35, Rom. 13:9)—forever (Matt. 10:22, Psa. 113:2).
5. Then God’s Holy Spirit will establish a saving relationship with those who freely accept Him (Rev. 3:20) that will eventually achieve heaven when by means of persevering in learning Truth/God’s Word/sanctification everyone cooperates fully with His will (John 14:6, 17&26, Rom. 8:6-17, Gal. 6:7-9, Eph. 1:13-14, Heb. 10:36, 12:1, Jam. 1:2-4).