Well, actually, point is, you can't just drop a video file into an ISO and expect DVD backup software to know what to do with it! To the DVD software, that video file is just "junk", just like those autoplay things (InterActual player, etc). It's not DVD video, so it (sensibly) throws it out. If that's all you "burned" to the ISO, then the whole ISO is meaningless to the program!
ISO is just a container for a virtual disc. You have to put something meaningful in the ISO for anything to be able to use it! Your first (and possibly, "only"?) step would be to look up some video-to-DVD software like ConvertXToDVD, but discussions of how to use, or where to obtain that software is beyond the scope of this forum (and if I understand correctly, not permitted). The software you've mentioned in your original post is used for DVD-to-DVD backup only, nothing else (not video to DVD as you're trying to do).
But, if you've got questions about using ImgBurn to burn your final nondescript "files" (*cough* the output of your chosen converter) to a DVD, then we're all ears