I don't think the chief has that much influence over the shaman considering that he contacted another tribe/warriors in his back and the plague that happen later would still prove him "right" that the Nords are harbingers of doom.
Again, you need to better remember the manga. The shaman Miskwekepu'j did not contact and organize the other Lnu tribes behind the back of Chief Gitpi. Miskwekepu'j gathering the other Lnu tribes occurred after Chief Gitpi had died from the plague (and on his deathbed Chief Gitpi requested that Miskwekepu'j take care of Gitpi's surviving family). The few remaining survivors of the Gitpi tribe turned to Miskwekepu'j for guidance after that.
And yes the plague (and/or any epidemic causing disease) would still be inevitable, but how Miskwekepu'j, the Gitpi survivors, and other tribes responded to the spread of disease could have likely been significantly different if Ivar hadn't cut off Miskwekepu'j hand and completely soured relations between the Vinland settlers and the Gitpi Lnu tribe.
Historically, you only needed 1-2 months of training with a crossbow to be considered "battle-ready".
You needed years with a sword to reach that point.
You arguably need years of training with a sword to become competently skilled, but that's not what I am talking about. I am talking about the much more immediate short-term, which is why I I said "minimum competency", meaning that any unskilled person can liably caused damage or kill someone just by having and swinging around a sword (which isn't the same as one being able to do it well, to be clear). While something like a crossbow, that requires a greater deal of learning in the immediate short-term just to be able to operate it. Most people cannot pick up a crossbow and pose an immediate danger in the same way someone who has just picked up a sword can pose an immediate danger.
Hild doesn't have any crossbow, she own a rapid-firing crossbow which is way overkill for the purpose of hunting, it's the equivalent of owning a semi-automatic rifle for hunting in modern terms.
Even assuming that a single shot has lower power than a proper crossbow (and we don't know that), it's offset by the fact that having 2 bolts in your body is going to hurt as much, if not more than just one bolt from a normal crossbow.
And it doesn't answer my question as to why Hild get a pass but not Ivar despite the former owning a much more dangerous weapon.
Hild's crossbow still isn't a tool solely created for harming other people, that's why she gets a "pass" (as did anyone who wanted to bring an axe, bow, spear, and/or knife all of those tools/weapons were okayed to be brought on the Vinland expedition). The fact that Hild's crossbow (or any other tool) has the greater capacity to be more effectively dangerous to people than a sword does is not point and/or why Thorfinn banned swords. The point had to do with how swords are a tool created for the primary (and basically sole) purpose of harming another person, the fact that a sword (similar to automatic and semi-automatic firerarms) has no other intentioned utility gives it a symbolic meaning and power that other tools don't have.
You're missing the point: you can kill with about anything, you don't need dedicated tools for that, they just make the job easier and ultimately, it's the people that kill, not the tool.
Of course one can kill with just about anything, even the manga itself acknolwedges and goes over that fact. You're the one missing the point that dedicated tools (whose only utility is harming other people) making it a lot easier is a big and meaningful deal (both narratively and in real life). As I stated before it's a huge part of why people react differenty to someone lugging around open-carrying an automartic or semi-automatic firearm, than someone who is just lugging around a hunting firerarm. The fact that a tool has nigh exclusive utility dedicated to harming another person and makes the job a lot easier is actually a big and important factor. It's part of why the Cold War arms race existed with nuclear weapons.
True but ultimately, the sword is "only" the greatest prize amongst many other iron "artefacts" which is why I think the Nords would have been attacked sooner or later.
There's also the fact that farming would allow the Nords to have a better and faster demograpic growth than the Lnu, which would certainly scare some tribes.
Nothing the narrative indicated that the Gitpi Lnu were scared about the idea of of farming or the Vinland settlers having greater demographic growth. In facrt a number of Gitpi Lnu like Plmk were interested in learning and adopting farming from the settlers.
The presence of iron tools (which the Gitpi Lnu were already begining to acquire some of through means like trade) only became motivating factors for attacking the Vinland settlers after everything else first went to shit. The mere existence of iron tools by themselves did not make an attack on the Vinland settlers a gauranteed inevitable thing (even Ivar's brother Styrk acknlowedged how the the vast majority of the Lnu were uninterested in war), the manga has literally depicted how all this other bad stuff had to happen first for the existence of iron tools to become a motivating factor for attacking the Vinland settlers.
I wouldn't be so sure, remove the sword but keep Ivar, do you think he would still have attacked the chief even without a sword? I think he would still have because he wants to be seen as a tough guy, he would just have used an axe or any other iron tools they have instead.
It is very possible that he may have, hence why I specified Ivar AND his sword, not just his sword.
The symbolic power and meaning of a sword is still relevant though as the symbolic power of a sword is part of the very reason why Ivar was so dedicated to smuggle his sword to Vinland in the first place and wasn't satisfied with just axes, spear, knives, bows, etc. and other tools.
The raider leader current goal is the sword but that goal itself is only a way for him to become stronger.
Even without the sword, the Nords still have better version of every tools the Lnu have, there's no way he wouldn't be interessed in a knife that pierce better than any knife he has ever seen or an axe that cut better than any axe he ever owned.
Ga'aoqi already owns a metal knife (and even then expresses no interest in getting more for himself, chapter 206 literally shows that). Which is just further evidence for how Ga'aoqi's primary motivation for risking and going on an unauthorized raid (and potentially exposing himself and his men to the risk of infection) was to obtain a sword. Which again is part of my argument, that without the presence of the sword, Ga'aoqi' would have been far less likely to decide to organized said unauthorized raid.