Sorry to hear that you are going through a difficult time. I can really understand that these questions go through your mind and make your heart feel heavy. Its hard to see a loved one suffer with the difference between how the feel they are and how they are supposed to feel according to the people around them.
I have been talking with a group of young people and friends (younger then me or my own age) who are gay as well. Both guys and girls. From what i hear and see i can not say anything other then that i strongly believe that it was not their choice to become gay and that they not even became gay but that they have been gay from the moment they where born. its not something that has grown upon them when they where little or when they where teens. Its just how they are.
I dont think being gay i a sin. But i do think that acting to it ís a sin. It states clearly in the Bible that people of the same sex should not be behaving together as a husband and wife. And that why i cry for those friends. For to love someone and not to be allowed to act like it. And to know that, if the Lord doesnt takes this away from you, you have to stay alone for the rest of your life. That is so tough to go through that when you are young. Especially when the people around you, even friends and family, are disliking you and behaving violent against you because you are gay. Some times people act like that because they are scared or confused or just because its easier to go along with the majority of people who say its someone's own choice and fault to be gay. But whatever reason they have to act like that; it doesnt change that what they are doing is actually there own choice and fault.
Our Heavenly Father and our Saviour Jesus Christ both teach us to be kind to one another. To love one another. To help one another. Not to judge about others. Sure, we do have the task to warn eachother when we see sin's be done. But being gay is not a sin in my opinion. Acting according to being gay (by example getting in a relationship with someone from the same sex as you) is a sin from what i read in the Bible.
I dont know if this helped you in any way. Just know that i really hope and pray that you keep your eyes on the Lord and knows that your help comes from Him. He knows your son. He loves your son. And He is willing to help you and your son to follow Him. I hope and pray that the Lord Almighty will take the gay feelings away from your son. But in the meantime i'll pray that the Lord will show you and your son that He is the One to go to with the things that are giving you a hard time. Or with the people that are giving you a hard time
. Let this situation draw you closer to Him.
God bless you and your family.