I appreciate your lengthy response, and providing a link to an anecdote to serve as a discussion point. I will say your approach to this issue appears to be rooted in much more compassion than other posts on this thread.
That said, I cannot fully agree with everything you say.
You start with "affirmation" and talk about the dangers of affirming wrongful behavior. I agree, in certain instances. You provide an example of behavior, i.e. blowing life savings on the lotto, that is much clearly more wrong and detrimental than simply being confused about one's sexual identity.
I would therefore ask you: what is the alternative to "affirmation" in the context of transgenderism? The only real alternative I see to affirming someone's trans-ness is to deny it. That's not a healthy approach, either, and is another thing that would more readily push trans teens toward feelings of rejection, isolation, and suicidal ideation.
You talk about studies on suicide rates, but don't cite them. I am not sure we can automatically assume that studies on suicide rates can provide a clear path for us on this issue. Look, it's not easy living with the feeling of being trapped inside the wrong body, which is how I've heard the experience of being trans described. It does not surprise me that someone living with that wrenching internal feeling would probably experience severe depression and even suicidal ideation from time to time. If trans people do indeed commit suicide at greater rates than other groups, it only goes to show how badly these people desperately need our compassion, and not our judgment.
I read the link to Walt Heyer's story. It sounds like Heyer went through a rough time, and I have compassion for them. I guess what I would say in response is that one can readily find plenty of other positive, affirmative anecdotes of trans people on the internet that cut the complete opposite way. Here's a collection published by the New York Times: https://www.nytimes.com/interactive/2015/opinion/transgender-today/stories/chris
As well as my anecdotes from my personal life talking with trans acquaintances. For them, their experience post-transition was life-affirming. The small number of people who have transitioned and report later regretting it complicate the picture of transgenderism a bit, but we cannot allow the tail to wag the dog.
Bottom-line, I respect your arguments but I hope they are not a soft-pedaled and nuanced form of transphobia.