I don't exactly see the problem with comparing Kakashi's statement that Naruto's movements were so fast, in BM, that he mistook him for Minato. It speaks volumes on how fast Naruto has become. When you're compared with a teleportation technique. For Kakashi to even make the mistake of thinking it was Minato out there... Yeah, sure. BM is clearly near FTG speed.
And yes, I know FTG is not actual speed but just Minato reverse summoning himself.
And yes, as of now Minato's only offensive ability is the Rasengan. You can assume that he has other jutsu under his belt, but what are they? We don't know. That's not a sound argument at all. Because you can't just say that Minato has other offensive jutsu, probably does, but he hasn't shown any of them. How do you plan on saying Minato harms Naruto or is better/is more powerful than him when Naruto has made more variants to the rasengan than Minato.
Planetary, Rasenshuriken, Giant Rasengan, and doesn't he have some more powerful KCM/BM Rasengan now too?
And I don't think his chakra nature was confirmed. It could be seen that Kishi hinted at that it was wind. But we clearly don't know. And what of Minato's oh so impressive sealing techniques shown to us are capable of taking down a shinobi of similar speed, and this enemy happens to have more advanced forms of the users only known offensive jutsu?
RDS? Doubtful.
The seal he placed on Obito, that rids the summoners control of their summons? The toads would be neutral/aren't controlled by Naruto. Useless.
Minato is certainly not stronger than his son.