Might I suggest you consult with professional linguists and grammarians on this topic? They will soon disabuse you of this prescriptivist nonsense about 'singular they'.

No, it isn't. Gender neutral / non-binary people exist, and "he" is not the correct term.

They exist and should be respected, but represent a tiny minority. Changing pronouns for everyone to please that fraction of the population seems silly unless you’re addressing that fraction.

Language has always changed with time. The singular they is very well accepted today and has been for decades in most English speaking cultures. I find it interesting that some people seem to find it necessary to defend the older forms - not sure what purpose that serves.

No? "They" is not incorrect nor is it even confusing to understand at all?