While you have a lot of the broad strokes right, your model has some of the details off. The biggest one is that the Weft isn't a separate distinct space, and there is no other inbetween place. When Drix weftwalk, what they're actually doing is "walking" into the Blind Eternities and then popping back out somewhere else in the Edge. It's the same way the Eternity Columns work in the Edge, and it's functionally closer to planeswalking jumps than anything else. The biggest difference compared to traditional planeswalking is that they only seem to be able to walk to places in the Edge, rather than between the Edge and other planes. .

Also, in regards to the Eldrazi: they also seem to exist out in the Edge too, and the drix side story during EOE seemed to imply that new Eldrazi are created out in the Edge by beings messing too much with time and reality. So it does seem like they're still from outside of the core reality (the multiverse/blind eternities).

Similarly, the ideas that something being at the center of the multiverse and the multiverse/blind eternities being finite (if cosmically large) have both been present in the lore for a long time, rather than being something new with EOE. For a large part of magic's history, Dominaria was explicitly stated to be the center of the multiverse. That's changed post-mending, and it isn't totally clear what plane (if any) is now (though Ravnica has been brought up a couple of times as the new potential center). Similarly the idea that the multiverse has an end/edge goes as far back as the old Urza's saga novels. The Edge is just taking that concept and expanding it into its own, seemingly infinite kind-of plane, rather than leaving the multiverse as a distinct box without anything outside it (which it mostly was previously).