Unfortunately, a detailed response seems to require a thoroughgoing review of current Early Buddhism literature (Wynne, Hamilton, Vetter, Bronkhorst, and others as well), and a forum post is inadequate to the task. Additionally, mileage may vary with respect to perceived evidential strength.
I simply want to indicate, in this subforum in particular, that the Nikayas are not
homogenous; they reflect a long period of routinization, and this long before Theravada even existed. Therefore, the Theravada tradition is best seen as one attempt at understanding Early Buddhism; there were possibly as many as 15 other scholastic attempts, perhaps more, and the historical accidents which saw the survival of Theravada are not enough to recommend their particular exegesis in toto
, especially when modern approaches have seen some success in correcting hitherto unrecognized mistakes.