The sentences I highlihted are totally spot on: the speed of light represents, at the same time, an instantaneous moment of simultaneity. The entire universe exists on the edge of the "now" you speak of.
But you can ditch the rest of mumbo-jumbo about getting out of the spacetime fabric we all live in. All physical entities and processes that exist in the universe are precisely built from the spacetime relationships that interconnect their internal structures and communicate them with each other at the speed of light.
Time travel is impossible once you understand why the speed of light is the limit for any physical process or phenomenon we experience: as you said, the speed of light is instantaneity or simultaneity in disguise, and there's no way in the universe to "reverse" a sequence that is, in fact, a simultaneous ensemble of events with no causal order implied, or be faster than instantaneous (which, in fact, is aking to infinite speed or teleportation already).
Whenever light speed is involved in some process or phenomenon that we detect, we must understand some form of instantaneity or simultaneity is also implied.
The time intervals material observers experience are always "compressed" into single points of instant existence for the massless quanta involved.
Everything in the universe is built over and over again from the instant (but light-like) fundamental interactions unfolding each time, but each material observer experiences them as different emission-flight-detection processes at the speed of light through spacetime.
This explains entanglement, and from there, all quantum weirdness can be explained.
The light-like interactions that unfold each time form a network of instant relations that interconnect spacetime from past to present, stitching reality each time. All the massless carriers we picture as travelling through the universe at the speed of light are, at the same time, the instantaneous entangled connections that create the spacetime structure itself, the information exchanges that hold up reality and make it self-referential and consistent with all its past history automatically.
Entanglement is the fundamental principle that drives the universe.
I explain all this more throughly here:
https://quantumwormholes.medium.com/the-universe-explained-7df2cf8ced90
But although this view has great explanatory power, it also clearly indicates that there's no way to overcome the speed of light barrier, making time travel a physical impossibility, since only the light speed mechanism is the one available to experience "infinite speed" or "teleportation", and time (the objective time in which fundamental interactions interconnect past events to the present moment through the speed of light constraint) always moves forwards.
Deeply sorry about that.
