Are you still sticking to the story that he was on full afterburners. I don't think he can make that trip 730 miles away doing that.
How does anyone know he was defecting? The guy is dead. Did he notify someone before he took off? If he did that then why not notify South Korea and have ship waiting off-shore so he can ditch his fighter and they can pull him out? Why Russia? Did Kim teach his people that Russia was some Shangri-la? That couldn't be possible because the North Koreans are taught very little about the outside world and they live in heaven now. I know that's the story from South Korea because they don't want to make it look China was the destination since the guy didn't choose them first as a better choice to live. So many easier choices but he took the hardest one and on top of that costed him his life.
I'm guessing the pilot had very little knowledge of his fuel state; the Soviet-style GCI system means that a ground controller pretty much guides the aircraft from takeoff to landing. That means a ground controller will doing all of the fuel calculations, and the pilot has to just verify how much fuel he has onboard to the controller, who then makes the decisions as to what to do. So, the pilot isn't likely to have a very good understanding of fuel management (all he would pretty much know is that he only has a certain amount of fuel left, and he was running out); he may know some basic navigation (flying a certain heading, etc), and combat tactics, but very little beyond that. This is not like a Western style pilot, who would know a fair bit on fuel management, navigation, other technical skills that would make him a lot more independent than a Soviet-style pilot.
I doubt the pilot had ways of contacting the outside world; the North Koreans do their best to restrict access and contact to the outside world, and if caught, face a lifetime in a gulag. He probably knew from rumours that going to China was a bad idea because they would probably return him, and he probably knew enough from flying near the border and from rumours that the outside world could offer a better life.