I'm genuinely sorry that you and your child are in this situation.
I'm sure you've already done a lot of research but I would seriously urge both you and your child to make sure you understand the long term implications of puberty blockers, cross sex hormones and elective surgery.
I can't help but feel that this issue is a sign that society has actually gone backwards in terms of how we see men and women.
If your child believes they identify as the opposite sex, what do they think that means?
What do they believe a boy is and what do they believe a girl is?
Because the way I see it, there are only two possibilities.
Either you believe a boy is a child of the male sex, i.e. born with a penis, and a girl is a child of the female sex. Or you believe that "boy" and "girl" are both identities.
If your child believes the former, do they understand that no matter what name and pronouns they use, no matter what they wear, and no matter what superficial changes they make to their body, they can never ever change sex? All medical transition will do is turn them into a lifelong medical patient who will be dependent on drugs and doctors for the rest of their life. It will drastically reduce the number of people willing to consider them as a romantic or sexual partner, and it will in all likelihood mean they can never have children of their own. Will doing all these things really make them happier and healthier than trying to learn to live with the body they have?
If your child believes the latter, what do they believe the features of the identities "boy" and "girl" are? Boys like blue and girls like pink? Boys like football and girls like shopping? These are incredibly sexist things to believe. And completely false, because there are many, many people who do not conform to gendered stereotypes typically associated with their own sex. Why can't they just be themselves without seeking to make serious and irreversible changes to their body which have a high rate of complications?
I'm not trying to lecture you and I'm sure you've had many sleepless nights thinking about all of these things yourself.
But I do think the old "I'd rather have a living daughter than a dead son" trope is hugely worrying. I'm sure some trans identifying children do have suicidal thoughts. What is less clear is whether those feelings actually go away after transition. And there is plenty of evidence to suggest that children are advised on forums such as Reddit and other online trans communities to say they are feeling suicidal in order to frighten their loved ones into affirming their gender identities.
As parents we can only do what we think is right at the time. I wish you and your child all the best.