About the whole balefire-transmigration issue - which RJ explains in pretty detailed words - he never mentions or indicates that distance to SG plays any role. If that would play a role, it's not understandable why RJ didn't mention it in this context, because that wouldn't give anything away. He just says (and this was new information, not revealed in the books) that if a very small amount is used, the DO can theoretically still transmigrate someone. If one reads this answer one has to assume that distance to SG doesn't play any role but just the amount of balefire, because the DO can also otherwise obviously transmigrate Forsaken everywhere in the world; at least the Forsaken never mentioned that they are only "immortal", if they don't die too far away from SG (and in the end of TFoH, the DO's powers on all of the Westlands were anway very much grown, as seen by the unnatural weather). In the same way, I could claim that it plays a role concerning transmigration if you are a man or a women, if you are balefired with a very small amount of balefire, though there isn't any indication in this Q&A that this would be the case. Basically, the idea that distance to SG would be in any way important for the transmigration of a balefired person, is just unsupported speculation.

RJ and BS mention a few other RAFO limits and circumstances of death, except for balefire, which can prevent transmigration and weren't revealed yet. That can hardly mean a death too far away from SG, because following your logic, one would almost always be too far away from SG, and that is something already shown in the books.