You bring up some good points about the character changes. I can say that you have a right to be concerned about them as well. However, I think that I can explain the differences between TOS Scotty and SNW Scotty. TOS Scotty past was apparently altered due to temporal shenanigans, and like the Romulan operative said in the alternate past, time keeps pushing back and making sure certain people and events still happen, even if its delayed or pushed forward. Scotty must have been altered in some way to be born later.