This is mostly wrong, yeah. Those assumptions are, first off, wrong. I'm not sure what feats he's looking at, probably upscaling Dio from Tarkus' feat since Dio himself is practically featless in Part 1 iirc. And you can't really estimate calcs and expect them to have too much weight.
That LS logic does make sense, though he's ignoring the fact that SP yeeting the Empress' teeth is way higher
That is incorrect. We consider Awakened DIO stronger than Part 1 Dio, if I have to be honest I disagree but either way he says he's stronger than ever, and while his regeneration is weaker in Part 3, that's before he drinks Joseph's blood. Awakened Dio suffers one non-Stand injury and immediately regenerates it.
Stupid multiplier, "vampiric energy" isn't a thing.