Your teenage son has certainly navigated a number of challenges and obstacles to get to this point in his life. The journey to become the man God intends for him to be is just beginning, and he will have many more decisions to make as he seeks God's will for his life.
One process and procedure to navigate is his military registration with the US government at the age of 18. This is a big decision and one that requires seeking God, reading His Word, listening for His direction and holding a conviction based on his understanding of Scripture. As a church body, Pond Bank Community Church has typically held a peace and non-resistance interpretation for the taking up of arms and for military involvement. Several key verses for consideration of this interpretation are: Matthew 5:38-48, John 18:36, Romans 5:5, Romans 12:18-21, 1 Corinthians 6:1-8, 2 Corinthians 10:3-4, James 2:8, 1 Peter 2:23, and 1 Peter 4:1.
Upon your son's personal study and understanding of Scripture, he will need to move forward with his US Selective Service Registration within 30 days of turning 18. Should he decide to register as a Conscientious Objector (CO), he can find more information at the link provided below.