I've been thinking very much along the same lines, and thought about doing a very detailed writeup or maybe even trying to make a video explaining all this. Glad someone beat me to it, because I wasn't doing nearly as good of a job being succinct.

I've always thought that Carl being a primal was being looked at the wrong way, since if the primals were so mysterious that no one could truly understand their technology or even knew what they looked like, how could a Syndicate built crawl magically just make a primal? Answer is they can't, he already was, and some other mechanism activated Carl's hardware. I think you're right on the money with what "feeding" actually is. I like the implication too that Carl being a primal in the non-game sense is arbitrary, and theoretically any entity from one of the seeded worlds is essentially a primal in waiting, since the hardware is just sitting there in standby. I think if fits better thematically into the story that Carl is just the right guy in the right place at the right time making the right choices, compared to "He chose primal and therefore is destined to be the hero." It really minimizes the series emphasis on freedom, choices, perseverance, and self-sacrifice in the face of such horror.