No, it's not conclusive, but the science is all pointing in one direction.
No. As has been demonstrated on multiple threads by discussion of the science.
That's why you see such clear connections between pronoun use and mental health:
www.thetrevorproject.org/survey-2020/?section=Supporting-Transgender-Nonbinary-Youth
The deficiencies of that conclusion have already been pointed out to you.
www.researchgate.net/publication/288633039_Phantom_penises_in_transsexuals_Evidence_of_an_innate_gender-specific_body_image_in_the_brain
Here is the abstract to that paper:
How the brain constructs one's inner sense of gender identity is poorly understood. On the other hand, the phenomenon of phantom sensations -the feeling of still having a body-part after amputation -has been much studied. Around 60% of men experience a phantom penis post-penectomy. As transsexuals report a mismatch between their inner gender identity and that of their body, we wondered what could be learnt from this regarding innate gender-specific body image. We surveyed male-to-female transsexuals regarding the incidence of phantoms post-gender reassignment surgery. Additionally, we asked female-to-male transsexuals if they had ever had the sensation of having a penis when there was not one physically there. In post-operative male-to-female transsexuals the incidence of phantom penises was significantly reduced at 30%. Remarkably, over 60% of female-to-male transsexuals also reported phantom penises. We explain the absence/presence of phantoms here by postulating a mismatch between the brain's hardwired gender-specific body image and the external somatic gender. Further studies along these lines may provide penetrating insights into the question of how nature and nurture interact to produce our brain-based body image.
This is, quite frankly, the biggest load of nonsense I've read in a long time. You can't conclude anything about how the brain is wired from a questionnaire about phantom sensory experiences (which I suspect would be better classed as wishful thinking).
I've met the first author of that paper in a professional context. he is rather well-known for producing this sort of stuff.