1) Yes- the label is widely known but we first knew of it when Kyros said it which is all I referenced him for.
2) "Stronk brain-" Smoker was positioned in the narrative as a bait and switch on our perception of the Navy as readers/as the eyes through which Oda began to hammer the themes of greater forces at play/inherited will, following up on Mayor Woop Slaps words on Destiny post-Arlong Park.
The final barrier in the stories prologue/a huge impact presence (also- Luffy specifically thinks of "Smokey" as a motivator for learning Haki and is invested in their combat rivalry/cares for him as a friend, which is verbalized in PH).
Try and think of something other than punching;
3) Smoker is the first character to draw parallels between Roger/Luffy (two D's) and quite literally swore his life on capturing Luffy; making him his white whale.
Smoker is unique in the series for the fact that his plot is predicated on Luffy's pace; if we want to get meta then in Loguetown Smoker clued into Luffy being the protagonist and inserted himself into the narrative (rather than it coming to him).
Two D's that the story has tied him to and the fact that he parallels more of Garp than you're willing to admit and follows down his line from Garp's connection to Kuzan.
Your "D" sentence is still a stretch/poorly phrased without any actual moment in the narrative pointing to it.
4) Smoker has direct cause to be involved in Blackbeard's arc via Kuzan and the fact that he's intimately involved at each turn of the era/tied himself to Luffy's fate.
5) Koby didn't do shit; he looked cool but ultimately he was bloodied by a bunch of Kuja haki and rightfully would have been folded by Boa; Smoker on page in PH was shown as comparable to the Law/ Vergo and co. and was injured come Doffy.
6) Cool, except i'm not trying to downplay Koby like you're doing Smoker.
Does this picture give you cold sweats at night?
7) Koby's chapter title means he's finally got a plotline, yes.
It means nothing else (a major one, but still nothing that counter's Smoker, it's just a title).
8) Once again, we know nothing about what Koby actually did or how much genuineness was in BB's words especially with the framing "hero" had from Sandersonia.