all videos for this run are non-functioning

Indeed. I just checked here myself for the same reason. I did manage to find the run by kakusuko in 21:16 on niconico: nicovideo.jp/watch/sm29334494

Ma-chan only has ganbare goemon 2 RTA videos on his account. He does have a guide describing how to play this game in Japanese and it describes himself as the real WR holder at that time.

Only thing I could find as a possible reference to resterror's WR runs is their live broadcast of this game on the 5th of November 2013 (the date listed for the run on SR.com) but it looks like that was a 19:52? And the video no longer exists.