The Jaina parallels are interesting, alkthough not revolutionary. We know that the life stories of the Buddha and Mahavira have much in common, so it is not surprising that the stories of their nemeses would also have things in common; in fact it would be more surprising if they did not.
However, as for the thesis of rehabilitation of Devadatta, this is just wrong. It’s a misreading of the texts and a misinterpretation of the history. I wrote about this at some length some years, and I’ve reposted my old essay here on Discourse for your enjoyment!