The guy who needed help to tire Jack out over five days (not beat, just tire him out) while resting every 12 hours is on his level? No.
Denjiro can be on Jack's level or a little stronger. We need to wait for him, but the others definitely aren't.
Empty hype? Fodder are fodder, not a single named character exists. If anything, this downgrades Denjiro's reliability considering the ease of which Brook, Robin and Franky could impact the battle. Brook who was easily beaten by Perospero an arc ago.
Yes. The Tobi Roppo look good. This doesn't effect the standing of Jack or the other All Stars.
Meanwhile, the most we know at this moment is that Kaido's son isn't showing up. There's no hype or inference you can gleam from that.
BM has how many children who are trash? Like, 40 or something? There's the potential for Kaido's son to be something, but there's no reason to automatically assume he turns the current, established hierarchy of the crew on its head. That's wishful thinking.