Well you don't have proof that it wouldn't have killed Natsu either

at least I've got one argument to back it up: Happy intervened because Hiro didn't want to complicate that fight and make it any longer than it should. Why would I think transporting Natsu to his own dimension wouldn't kill him any more than it would kill the other FT members? Because the other FT members are weaker than Natsu? Well, that's true.
But who knows what laws govern Jacob's dimension? Are the characters somehow defenseless, incapable of using magic? Are they not? As you see, we're both assuming here. My assumption is that Jacob can kill Natsu in his dimension. My argument is that it's Jacob's dimension and if he's NEVER missed a kill and considering his MP is superior to Natsu's and considering he was capable of transporting a lot of people into his dimension... That all leads me to think Natsu would be pretty much done with.
If you want to think otherwise it's fine but give me proof that Jacob won't be capable of doing anything even if he transports Natsu into his dimension.
How is steel white, by that same token? It's hard to figure out. Some are going to interpret it as blood, some as melted metal. We'll have to see the anime to conclude anything.
With all due respect, implying the real/intended color of the knife is white because it is white in the panel is nonsense.
Lucy and Mavis' hair looks white. Is it? No, it's blond. Lucy and Jacob's skin looks white. Is it white? No, their skin is the color of skin. The background looks white, does it mean the walls of FT are white? No, The background was not important so it was not drawn/painted.
Now, why does my claim about the knife not being white have more weight than yours? Because I don't know of any white metal used for weaponry (and if it was 'painted' in white the real color would be uncovered upon melting) + because we've seen more seemingly white elements that are not realistically white (which backs up my claim).
Now, that in recurrent panels Natsu does not show any wound would be an argument that would back up your theory that he wasn't actually pierced. To me, the image makes it clear that he kind of was, but looking at the whole picture I may be wrong.
I kind of agree with you here. If we operate under the assumption that DF/FDKM Natsu may blitz Jacob (we can't know if he's fast enough so as to punch him before he claps), and if we're also operating under the assumption no weapon is going to work on him because his fire aura is going to melt anything that passes through it, then not only is FDKM/DF vastly superior to Jacob but to most of the verse. Wahl couldn't actually hurt him at all by that same token since anything he can throw at him is going to be melted, and energy attacks are going to be absorbed (most likely) as fire-based attacks... Heck, even Dimaria could freeze time, but she couldn't actually "kill" Natsu if his fire aura is still active/working after age seal.
On another note, Racer is faster than average, but Jet is probably faster. Racer can slow down time around himself so even Jet is going to be slowish to him.
WONDERFUL POST! Thank you