Autistic teen rejects support

Hi, I’d be very grateful for some advice or insights on how to best help my autistic teen. He is nearly 18 and identifies as a boy but is biologically female. He rarely leaves his bedroom and so has very limited experience of living as a boy and does not want to join any groups of teens going through similar trans and identity issues. He has ADHD as well as being autistic and occasionally takes medication for this but dropped out of school at 13 after we tried flexible study arrangements etc. Currently he is hostile to any suggestions or offers of assistance from his dad or me and has an irregular sleep cycle as well as very limited food intake. He does not want to go to college or get involved in any activities outside the home. I’ve presented the situation factually but I know that readers here will understand that this disguises huge distress for him, his twin sister and his parents and grandparents. Before puberty he was a happy, quirky child who was full of life and I am terrified to think that he will end up in hospital if he does not begin to engage with basic living requirements such as eating well and taking exercise. I’m clinging on to the hope that time and love will make things better in time but I would welcome any advice or shared experience that can make that hope a reality.