4:56 That would make Nappa an anomaly as well we do see a lot of Saiyans in the first Bardock movie but that's in comparison to other Saiyans for the most part so not really a good gauge I guess
23:39 In the original series it was a heart virus he got while on Yardrat for some unknown reason it took 3 years to appear in this timeline (maybe it was hastened when he fought Freeza in Trunks timeline idk) so while they had the medicine the symptoms never showed up so there was no reason to take the medicine
31:39 Originally they were slated to be the big bad but he editors basically said "So wait the big bad is an old man and this fat clown looking guy" so he pivoted in another direction
I believe Vegeta just wants to prove that he's the best his pride won't let him be anything less than that.