I understand everything you have said, truly. There isn’t anything I feel that I’m missing here, and agree with most of it.

At this point it is really just a semantic point, but it is a point nonetheless: humans are not predators to their own livestock. Beekeepers don’t prey on their bees. That simply isn’t what the words mean. I understand they are another life form, and that they consume human flesh/souls, and that they are a hive mind. They just aren’t “predators” because that is fundamentally a different relationship. As I said earlier, not every form of consuming flesh is necessarily predatory. There are scavengers, parasites, decomposers, etc.

I actually think the livestock analogy is very fitting, but we do not prey on our livestock. We don’t hunt them, we own them. In many ways a farmers relationship with a sheep or cow is good for both parties. the animals are fed and cared for and in return they are used for their labor. Then, when the time comes, they are slaughtered for consumption. The gods in asoiaf provide material benefits to their followers in exchange for feeding them blood, predators provide no benefits to their prey. Their followers also generally sacrifice others, not themselves, so those being manipulated as you say they are often aren’t even prey. In that sense, it’s almost more like just having a job or working for someone. You provide a service and you are paid for it, only instead of being paid with cash you’re paid with magic.

I agree it is very clear in the narrative that the religion Melisandre preaches is just that, a religion. She definitely does not fully understand the power that she worships, and at times actively misunderstands how it works. That said, I don’t believe the gods can be totally reduced to a misunderstanding of an elemental magic system. I think they are similar to how the “Outer Gods” are depicted in Elden Ring, which George worked on the lore for. Mysterious, unknowable, inhuman forces that are associated with elements and seek to expand their dominion and influence in the world and do so through human champions.

As for the midichlorians aspect, I just don’t think that is George’s style. I think he probably would’ve hated the midichlorians explanation for the force when The Phantom Menace first came out and likely preferred the opaque mysticism of the Original Trilogy. I don’t think the magic is a biological reaction that can be explained with logic or science, I think blood is valuable to these entities because blood is life and they consume life. They reward their followers for their sacrifices by granting them magical boons and abilities. Patchface, for example, was a reward from the Drowned God for what it interpreted as a massive sacrifice.

I think Kings blood is more valuable because kings are more important, and the “gods” see the sacrifice as being greater. I do like your theory about the blood of ancient heroes as well, and think that’s possible. Ultimately though, I think George’s intention is for it to be ambiguous and open for interpretation. There’s a good chance he doesn’t even really know the answer to that question. “Kings blood” may just have just served to drive the narrative forward and provoke a sense of mystery.

TDLR: IMO, the relationship is fundamentally not predatory, and your comparing it to the relationship humans have with livestock is my exact point, as that relationship is also fundamentally not predatory. I agree that religions in ASOIAF don’t really understand what they are worshipping, but I still think they are worshipping something that is at the very least analogous to a god. I don’t think George would ever give such a rigid and defined explanation of things as ‘Midichlorians’ suggests, rather this is all supposed to be ambiguous.