Captain Cadaver said:
It may have been the speed of the attack that allowed Vegeta to make his judgement.
Characters have been able to assess the strength of others when fighting far weaker opponents as early back as Yamcha being able to tell Jackie Chun had gotten strong enough at the 22nd TB compared to his previous appearance that this would be an interesting tournament just from seeing him oneshot worthless jabronis. Whilst the difference was far less battle power wise, it is pretty much the same as far as the narrative goes.
Maybe, but power and speed don’t always correlate. It’s also worth noting Vegeta was unable to track even Gero due to relying more on Ki sensing than his own eyes, so the mere fact he could see Dabra’s movements would imply he wasn’t trying at all.
Though it was Goku who raised the comparison to Cell saying that Dabra probably wasn’t at full power killing Kibito, so the two aren’t mutually exclusive here.
I’m not sure if these situations are comparable. Yamcha specifically referred to Roshi polishing his moves, which is more about skill than power.
I don't think Vegeta's feelings would've mitigated his boost, considering Babidi's possession simply draws a person's power beyond their current limits and his possession of their will is just an additional effect on most.
Looks like the other way around to me. Babidi first possessed Vegeta and then unlocked his power, and Daizenshuu 7 says they’re different steps of the same spell. If step one is hijacked, then so should step two.