Worried Stepmother

It’s my first time using this or reaching out for any advice on this subject. I am concerned about some things going on with my stepson. I have been in his life for almost 7 years (he just turned 14). His father has sole custody, but because of his work, my husband’s mother has had him for months at a time all his life. He stays with us when his father is home, but stays with her when he is gone. He did stay with me for a little bit when he was younger and we became very close. I do feel his grandmother interfered with our relationship because she is overly possessive of him. The thing that is concerning me is; about a year ago, my stepson came to me and asked me “what I would do/think if he were gay”? I was beyond shocked and ill prepared for the conversation. I am a Christian, so there is a matter of it being against my personal beliefs. I told him exactly what I thought; I love him and there is nothing in the world that could change that. I told him I wanted to be there for him with whatever he needed. I found out a few days later that he had been chatting with someone online and some of the material was pretty explicit. One message (out of hundreds) was about how to shave his private area and how to be a “bottom”. I didn’t want to tell his grandmother about our conversation, but he refused to stay here until I could get us into counseling to make sure he wasn’t a victim of a sexual predator. I told him why he had to tell his grandmother and let him choose on telling her so he could be monitored or stay with me until we could get counseling. Due to my limited online rules, etc… he chose to tell her. I made him an appointment with a psychiatrist that did observe the messages and talked to him and felt that both parties were equally responsible for the conversations and he was not being victimized. His grandmother and father refuse to believe he is gay and have not gotten any type of counseling for him. Right before school let out, some kids noticed that my stepson was shaving his legs and being “touchy” with another male student. I asked him about his feelings and he said he still felt attracted to males. I have not told anyone about that conversation, because I do not want to betray his trust. A few days ago, his grandmother said she had a talk with him and he told her he did not have those feelings anymore. He knows his grandmother and father will be devastated if they know he is gay and I feel he is lying to her. My biological son is in the same grade as my stepson and mentioned to me that the majority of junior high students at their school have come to him and asked if his step brother is gay. I have not mentioned anything to my son throughout this whole thing and will not discuss it with him in the house. It seems that my stepson may be exhibiting behavior that others consider “homosexual behavior”. I am worried about my stepson because he has stopped caring about his grades and spends 95% of his time in his room and on some type of online entertainment. When I went over for his birthday, he didn’t even come out to eat with everyone. He actually failed 2 subjects last year. He is a super smart kid and used to be an A and B student ! I am so worried about him being depressed. I am fine with him trying to figure out his feelings, but it’s going way beyond that. So what would you do? Side note: his mother gave up her rights so there is nothing to explore there and I am the only mother he has ever had. I cringed writing stepson, but I didn’t want to use his name.