All current (genetic) populations evolved from Pleistocene populations. And Native Americans are quite a distinct group because as you noted they came here quite a while ago. Perhaps as long as 25K or as late as 12K ya.
Your time line seems to be correct, from what I know.
American Indians and the ‘’native’’ peoples of Mexico and Central America are really Asians and Asians, being raised on a different type of diet are adverse to alcohol because unlike Europeans Asians didn’t have quite the acclimation to grains as did Europeans which is why when American Indians and Mexicans get drunk they go ballistic.
Their bodies in effect are having a severe allergic reaction to the grain in the alcohol.