The funny thing about this is that, in BfA, none of the Azerite essence abilities deal arcane or some kind of Titan/Order form of damage. Every damaging ability, except one, deals Fire damage. The one exception is a shadow damage ability. I don’t remember seeing anything arcane in connection with Azerite since it became a thing, which is odd if Azeroth’s blood is arcane. Again, just as an example, we’ve seen heavily arcane infused areas. Big purple crystals and the like, purple everywhere. Titan Order magic doesn’t resemble that, and anything involving Azeroth resembles neither.
It’s a major plot point right now, so of course they haven’t just come out and said anything directly. But there is way more out there than just one cut scene at the end of DF. In all honesty, I think they have created some contradictory things recently because the story’s narrative has changed since 8 years ago when Chronicles 1 came out. Heck, once we got the whole “It was written from the Titans’ perspective” stuff, and especially when they made a new cosmology chart from the Brokers in Shadowlands (I feel like people sometimes forget that one), you can’t take any of it as definitive. So I just go by the breadcrumbs they give us and try to piece it together.
Most of the contradictions I see I chalk more up to the narrative getting more complex as years go by, and the impossibility of making every detail square with later stuff a decade later. Your only choice there is to retcon stuff or just leave it contradictory I guess.
I don’t think they are evil per se. I think Blizzard has just hit everything with the morally grey bat. By morally grey, I mean they went down the road of “everything needs to be balanced.” Firim’s questline in Zereth Mortis was where I feel like they tried to dive to the heart of it. The cosmological forces need to be in balance, and it will be bad if the Titans gain influence over the Prime Worldsoul because the balance will be tipped in Order’s favor. Heck, if ANY force gets/uses Azeroth, it breaks the balance.
Firim’s writings didn’t suggest any of the cosmological forces necessarily know that. They are all just doing their thing. But, winning at doing there thing isn’t necessarily good.
Is that really true? Doesn’t the current lore kind of point to there being a Zereth for every force, and the First Ones created the beings there? The Eternal Ones of the Shadowlands were created in Zereth Mortis, so it isn’t a stretch to think there is a “Zereth Ordus” or something similar where Amun’thul came from.
It’s worth noting that, as far as I remember, the Eternal Ones didn’t know that they were created there. They had vague ideas of the First Ones, but they weren’t exactly aware of the true nature of them or Zereth Mortis.
It is also worth noting that it doesn’t look like their creation is exclusive to the Zereths. Pelagos took Zovaal’s spot as Arbiter outside of creation in a Zereth. Although the key part of the Arbiter still has its origin there (I forget if the thing in the Arbiter’s chest had a name).
Eh, Old God half-truths 
Those are all possibilities. I forgot about the arrow line, seems to me to line up pretty well with Alleria (arrow finds its mark) and the defeat of Xalatath (the last fetter will fall away). Old God riddles are the most fun.
Your statement reminds me of the fun theory from back in the day of Azeroth being influenced by Azathoth in Lovecraft’s works. Blizzard has obviously had a lot of Lovecraftian influence.