"Only in VERY recent times has it been revealed" autism is not demonic possession. People's suffering is pretty strongly related to how they are treated. And considering modern people have been strongly discriminatory against transgender people, it is pretty easy to see why trans people have issues nowadays. 

We don't have suicide the statistics you want and thus can't assume. If you want to know what it was like, consider that in the past transgender people have been committed to asylums. It was illegal. 

And again, it is a fallacy to assume that because we can measure suicide better now that it never occurred in the past. The absence of evidence is not the evidence of absence. So where is your evidence that 200 years ago transgender people were all happy and healthy? You don't have any. 

Your assumptions also don't take into account the effects of hate and discrimination which you yourself are perpetuating. Visibility of transgender people is higher than ever before as well.