I would have loved to read the paper you wrote. About separating the Axis partners, well, I agree it would not seem likely but that doesn't mean it would be impossible. The Imperial Japanese Navy enjoyed strong ties with the Royal Navy and that could've been used as a conduit for backchannel talks. I know it's only a possibility, even a slight one at that. But this is a what-if, I mean an alternate history right? It's a shame that Roosevelt was right about using the threat of an oil embargo to force Japan to take a certain course of action.