I think you missed a few steps near the beginning. When Rick and Morty C-137 jump at the end of Rick Potion #9, he says he wont be able to do this too many more times, which hints that he has done this before. We have no clear indication that C137 is where Rick is originally from, only that Morty C-137's Rick has been missing for 10 years at the point where our Rick returns...which strongly argues for the idea that C-137's rick is long gone or dead, and that our Rick opportunistically moved in on C-137. I also think that the way in which Rick dotes on ALL copies of Beth (he does so in C-137 and in the dimension he moved Morty to after C-137, as well as other examples) is an indicator that whatever started Rick on his travels probably killed Beth in his original dimension, making every version of Beth precious to him. Further his disdain for Morty, and the way in which he coldly uses him over and over makes me think that Evil Morty is our Rick's original Morty, and that Evil Morty may have been involved in his own mother's death...