As I think about the current diagnosis and the earlier symptoms, some things now seem to make sense. I think that the bubbling I was seeing in the overflow container was actually exhaust coming out of the coolant from the blown headgasket rather than from overheating. That would explain why the fan never turned on despite multiple attempts to fix it but still seeing bubbling in the overflow. Since I do not know how hot the actual coolant was at any time, these are all mere guesses, but it seems to make sense to me. I'll update it there is anything more to add. Thanks again for all of the help!