Hi OP, that's some really great advice from TwoLoons there.
I have an autistic daughter who seems to have come out of the other side of being gender questioning.
When she first told me about her feelings (of confusion and distress) I told her that I would help her explore whether she really was a girl - and that I would learn how to do this and who we could go to etc - but that in the meantime, everything she did to alleviate her feelings of distress about her body had to come from the position of being biologically female i.e. no change in pronouns... no trans-aligned practices of any kind. For example, it was sports bras not binders to hold down (and hide - this was important to her) the unwelcome development of breasts. She had her hair cut short at about 13/14 and has worn clothes from the boys' aisle since childhood. She didn't want people looking at her "as a girl". I supported her with this need but the line was clear: you are a biological female. This is a physical reality. When she asked for puberty blockers at the age of 13 we looked into it, saw that the NHS at that time said "the impact on the developing teenage brain is unknown" (paraphrased) and said no. We told her we didn't want her brain being experimented on. She accepted this.
I joined an LGBT trans parents' group so that I could listen to the experience of parents whose children had transitioned. It was very clear that every parent in the group loved their child very much and wanted the best for them.
I also found other viewpoints. I second TwoLoons' advice that asking for this thread to be moved to the Feminism Sex and Gender board might get more traction. FWIW I have no idea if I'm a feminist (I used to assume I was but I am not into feminist theory etc) but I found that board incredibly helpful to understand the difference between sex and gender identity during my research. There are teachers and other professionals who comment on threads about children and I learned a lot about safeguarding on that board.
I also looked at FB and YouTube to see the kinds of things my daughter might have been looking at. It was important to me to understand the information my daughter was seeing that made her wonder if she really was a girl.
I apply a safeguarding approach whenever my daughter meets a new health professional or joins a new club. I have a document with her safeguarding needs written down (by me) regarding the conflation of gender identity with autism-related puberty distress. If you believe your son may be gay or bi, the conflation of gender identity with sexual orientation (LGB) may be more appropriate here. LGB Alliance has lots of info on this.
I have also included links to changes in education, healthcare and law regarding gender identity for context. It's a great conversation opener and helps me to ascertain how likely she is to be protected from gender identity coercion in any given scenario. In most cases this coercion comes from a place of kindness, where the adults asking everyone their preferred pronouns etc don't realise that they are signposting the idea that everyone has a gender identity that could differ from their sex to children who may be confused about sex-based stereotypes and/or uncomfortable about their developing bodies/emotions and are looking for answers about who they really are.
I've only had one occasion where I was told my views were abhorrent and one situation where a health professional read the document, acknowledged it and then tried to get my husband out of the room (by asking my daughter several times if she wanted him to leave... despite it being a routine medication appointment, with a new doctor) after opening the appointment by asking her about preferred pronouns. On all other occasions, this document has been a door opener to positive interaction. For me, it's been a game changer in navigating this with professional support. (Unsurprisingly?), my daughter's distress turned out to be related to her autism not a hitherto stifled true authentic self.
The only other issues I've had were with the school. They considered me a danger to my daughter. A story for another day/thread.
Finally, I would say that if you do move your thread to the feminism board, it's worth being aware that there is a potentially unresolvable juxtaposition between the (predominant) support for a "belief in biological sex" (as this has won court cases under equality law) and safeguarding. Safeguarding requires a neutral position, where biological sex isn't positioned as a "belief". Thankfully the original case-law impacting court case (Maya Forstater's) also won protection in law for those who don't believe that everyone has a gender identity - this is the truly neutral position I.e. those that believe gender identity exists and those that don't, similar to belief in god/Allah versus atheism. There are lots of threads on the feminism board exploring this too. I found that getting my head around gender identity as a belief (the idea that we all have one that can differ from our sex), and that I ultimately realised I don't hold it, was fundamental. To this day, I still accept and recognise that others do believe in it and that that's OK. What's not OK is positioning that belief as fact.