Firstly, there's a joke about three people who applied for a job and they were all asked what 1+1 equaled. The first two replied "2" and were rejected. The third replied, "What do you want it to be?" and was hired. The Pew Research that you reference cannot be interpreted as transgenderism diminishing with age. The only way to reach that conclusion is to follow a trans person from when they first felt that way and through their life and see what trajectory it took! What I can surmise from it is, many older people have a more conservative attitude. One of the biggest MYTHS and it is a myth, is the old saying that, "So and so has turned gay." A man doesn't marry a woman and then suddenly decide he's gay, what happens, and this is more common amongst today's older folks, is, now let's say we take a gay man who's aged 75. Say, he was a 19-year-old college student, who married a woman when he graduated age 21 (let's say he married her so that he could avoid going to Vietnam, but he loved her nonetheless). Tiem progressed, they had children, but he suppressed his true sexual orientation, but at 51, he could contain it no longer, and he and his wife divorced and he entered a relationship with another man.
Now we come into the claim of suicide. Let's take some of that into consideration. What people have to remember is, when a person transitions, they are still the same person as they were. They just present socially differently. What I mean by that is, most times they still have the same interests, the same opinions, the same beliefs, but Joseph has become Josephine, for example. Part of the reason why SOME may suicide is that they find they're not accepted as readily as they hoped. But MOST trans folk, post-transition, find that their mental health improves.
You say love is rooted in truth, and let's take that as a point. Sometimes, when a person is in a new relationship, they'll say, "Oh, I love this, or I love that," and reality sets in and they find that they don't really like what they said they did. They just wanted to make a good impression. Facing a truth, in the case of a trans person is NOT, and I repeat, is NOT, about standing them in front of a mirror and saying, "You are a man. Accept it." It is about helping the person accept their reality. And if their reality is that they want to transition, it MUST be respected!