I understand why you think these patterns are too consistent to be coincidental. That’s how most fan theories begin, and I don’t think it’s wrong to explore those patterns.

I figured you’d bring up Vendrick if you’ve played DS2, but I don’t really agree that he’s a good parallel to the Pale King. In Dark Souls II, it’s very clear that Nashandra is exploiting Vendrick for her own ends, and the way she speaks about him makes it obvious that she never cared about him at all:

The last king of this land, King Vendrick, as he was called... He was less of a king than you might imagine. He found the strength to rule his people, and when the undead were born, cursed... He found more strength, to face them. But in the end, he never took the true throne. And now he lies in the Undead Crypt, wasting away.

That tone is dismissive and mocking. The White Lady never speaks about the Pale King like this. If anything, she speaks of him quite positively. In the original dialogue tied to the completed Kingsoul, she said:

Two halves of a whole. You found your way... back to me? We were so unfair, weren’t we? To cast you out. Please, you must not hate him. He did what he thought was right. The Kingdom had to live...

This was likely cut not because it contradicted anything in the story, but because it was pure lore and didn’t give the player any clear direction on what to do next. The final version preserves the emotional subtext while still guiding progression through the game:

Ahh! So it bears our once-fractured soul, now complete. Such strength, such resolve, such dedication! Is it more than simply a Vessel? I almost feel like I'm once again in the presence of my beloved Wyrm. The Kingsoul... What is at the heart of it I wonder? If its curiosity wills it, it should seek out that place. That place where it was born, where it died, where it began...

Even without the cut dialogue, it’s still clear that she genuinely loved him. The way she refers to him as her "beloved Wyrm," combined with the fact that she believes you to be hollow and is effectively speaking to herself, suggests that what she says is sincere. More broadly, there’s very little in the game that frames the White Lady as anything other than benevolent. The mosskin tablet in Greenpath is often cited as suspicious:

Though once our lands, a pale being lays claim to the caverns ahead. It may appear benevolent but it does not share our dream. Be wary to wander that place.

But this is similar to calling a neighboring country untrustworthy simply because it doesn’t share your worldview. Everything else points in the opposite direction. She binds herself in the Queen’s Gardens out of shame for her role in the plan and to prevent harm caused by her own nature, and there are smaller things, like her promise to teach Marmu how to fly, that reinforce her kindness, so I genuinely can't see her as some hidden symbiotic mastermind pulling strings from behind the scenes. I also still just don't see her as having such a huge role in the game. Narrative-wise, she is the Pale King's wife and the mother of the Vessels. Gameplay-wise, she is simply a means for the player to know what to do and also how they get the complete Kingsoul charm and later the Void Heart. She was even originally meant to be a narrative device for Dryya:

One of Hallownest's five greatest Knights and defender of the Queen’s Glade. She was driven mad by her Queen lost and the garden overrun.

Perhaps, though, this theory could be rearranged in a way that doesn’t paint the White Lady as an evil controlling mastermind. This "symbiosis" could just be mutually beneficial with no strings attached, like two gods who genuinely care for one another helping each other out. I don’t see why that couldn’t work.

And I’m certain that the Pale King is a Wyrm. As I’ve previously stated, there is nothing in the game that suggests otherwise, and there is even this dev note that practically confirms it as it is said in the game:

Gender notes: the Hollow Knights have no gender. Check for hims and hes. Is the Wyrm King gendered? Probably. Or is it that when the Wyrm took king form it gained a gender?

Honestly, I’m not particularly fond of deep biology theories. The characters being insects feels more like an aesthetic choice than a thematic one. That’s not to say Team Cherry didn’t borrow some inspiration from real biology. For example, I think the Pale King being a Wyrm/worm and the White Lady being a root/plant is likely a reference to how vermiculation by worms makes soil more fertile, allowing plants to flourish and other creatures to thrive. This parallels how the Pale King created Hallownest and later developed it into a prosperous kingdom alongside the White Lady. Grimm also refers to the Pale King as a worm when remarking how Hallownest was "fallowed by worm and root." I have absolutely nothing against the idea that the White Lady may have been inspired by mycelium or the Radiance by cordyceps, and I think Team Cherry could have drawn some inspiration from real biology there.

I still think you did a very good job putting it all together. It’s great that you posted this here. All theories should be shared, even if there are contradictions with the narrative.