Did Ambedkar have supporters and allies from the upper castes?
He did, and it matters for anyone tempted to read his struggle as one caste against another rather than as a fight over a system. Caste-Hindu reformers stood with him at moments of real risk — the Mahad satyagraha of 1927 drew support from beyond the Depressed Classes — and across his life he worked with teachers, patrons, colleagues and political allies who did not share his caste and did not need to in order to share his aim.
This fits the shape of his argument rather than cutting against it. His case was never that upper-caste people were the enemy; it was that a system of graded inequality harmed the country and had to be dismantled, and such a case naturally drew allies from every quarter that could see the harm. He wanted the wall pulled down, and was glad of any hands on the rope.