This person's 'weirdness' is, I think, a neurodivergence which I won't offer a diagnosis of.
I don't think a gender transition will make this person whole, this person will just be a weird person who is also trans. The old problem will persist but now he (maybe she or something else later) will have additional side effects and other baggage not to mention lost opportunities such as not being able to be a father.
The goal is not to make yourself whole and even if it didn't work out, they could de-transition (and should be supported in doing so). Stopping HRT (as long as you at least temporarily take HRT in the opposite direction to kickstart things again) has little in the way of long term effects.
> not to mention lost opportunities such as not being able to be a father.
This isn't true. Even if you stay trans the entire rest of your life you can still often have kids. This goes for trans women, trans men, and nonbinary people. Generally at worst you'd just need to supplement with some hormones to support fertility but often even that isn't necessary.
But supposing someone de-transitioned, fertility generally returns completely or near completely within 6 months to a year.
The only case where you can't "undo" any degree of loss of fertility is with an orchiectomy (testicle removal) but even then the standard procedure is to preserve sufficient semen in cold storage for future use.
I don't think a gender transition will make this person whole, this person will just be a weird person who is also trans. The old problem will persist but now he (maybe she or something else later) will have additional side effects and other baggage not to mention lost opportunities such as not being able to be a father.