Welcome! It's true that the Society's arguments against evolution are dubious and facile. They serve well enough for those who want to keep believing in the religion, though.
On the subject of the organization and on mental issues among Witnesses, I think the two are basically one and the same. The personality of an organization is derived from the founder/leader and trickles down through levels of management. So you have to look at the top and ask yourself what sort of people have led the organization and picked their successors.
The most important were probably Russell (a practicer of numerology, and a celibate though married), Rutherford (an angry, cynical contrarian and egomaniac), Knorr (a cold businessman, also another married celibate), and Franz (a very aloof man who inherited Russell's flair for numerology; a life-long bachelor).
Since the organization is a high-control group (i.e., anti-individual), its followers are expected to adopt somewhat uniform personalities, with an emphasis on subjugating the self and following orders, and holding beliefs which reflect the personalities of the leaders. How could anything healthy come from such an organization? It's no wonder that born-ins are a weird bunch of people. That's besides the fact that the conspiracy-theory folks and assorted societal misfits are drawn to the religion as converts.