Was it really the raw video or an edited one? Also, i reread ch 49 through 54, never saw a blowjob scene or instance. The rest could be faked if edited properly, just like with mitsuzuri and Ryouga. Even being naked and the kiss itself. Like, a dildo with edited pixel art, like with these futanari in JAV?
Didn't read 55, but if she planned the SD scenario, wouldn't it be bc she and Shingo are accomplices? And discovering the truth about Momonga channel could be problematic for both and their spouses? Shingo's wife don't know, and it could hinder their relationship. If they edited the videos, put them back at the SD card and use it as lure, however, would be safer and more dramatic.
I mean, my line of thought is that her Red flags are big and obvious, and the DNA test talk was too much of a safeplay anyway, so why risk? Personaly, i still think it's either a test of to see if he cheats.
But at the end, i really think Shingo is not her "true" lover or the father of the child. Too obvious as of now. But maybe Sousuke's kouhai, the one who showed him the video in ch1? That seems appealing( guy has been laying low for the entire story run until now).