No. We really have no idea what is going on. We only know some basic psychology about it (holding 7 things in short term, etc.) If we knew something about implementation, we could implement human-like memory.
Literally nothing you posted surprises me in the least, and literally none of this work shows that we know anything at all about how memory is implemented. Perhaps read some of the many takedowns of so called "grid cells" which show that it is completely unsurprising and not at all interesting or noteworthy that activity in some parts of the brain correlates with location information. The important questions always remain unanswered.
We know a fair bit about how cognitive maps work in 2D and 3D Euclidean environments. We know damn little about how nontrivial manifold structure can be learned, particularly in spaces with more than three dimensions.
spatial cognitive maps used for navigation are extendable to arbitrarily high dimensional spaces for abstract concept representation, using pretty much the same machinery.
There is a ton of work on this, both theory and empirical evidence, here are just a few:
