Many theories I've read about Dark Energy has sounded like stories made to fit some observations. The funny thing is that sometimes when I read old stories (mainly coming from India/South Asia) there are mentions of the amount of of Earth's expansion (being used as a measure of time) Your descriptions on "What is beyond our universe?" instantly reminded me of https://en.wikipedia.org/wiki/Indra's_net

Indra's net (also called Indra's jewels or Indra's pearls, Sanskrit Indrajāla) is a metaphor used to illustrate the concepts of Śūnyatā (emptiness), pratītyasamutpāda (dependent origination), and interpenetration in Buddhist philosophy.The metaphor's earliest known reference is found in the Atharva Veda. It was developed by the Mahayana school in the 3rd century Avatamsaka Sutra and later by the Huayan school between the 6th and 8th centuries.

Far away in the heavenly abode of the great god Indra, there is a wonderful net which has been hung by some cunning artificer in such a manner that it stretches out infinitely in all directions. In accordance with the extravagant tastes of deities, the artificer has hung a single glittering jewel in each "eye" of the net, and since the net itself is infinite in dimension, the jewels are infinite in number. There hang the jewels, glittering "like" stars in the first magnitude, a wonderful sight to behold. If we now arbitrarily select one of these jewels for inspection and look closely at it, we will discover that in its polished surface there are reflected all the other jewels in the net, infinite in number. Not only that, but each of the jewels reflected in this one jewel is also reflecting all the other jewels, so that there is an infinite reflecting process occurring.

If untold buddha-lands are reduced to atoms,
In one atom are untold lands,
And as in one,
So in each.
The atoms to which these buddha-lands are reduced in an instant are unspeakable,
And so are the atoms of continuous reduction moment to moment
Going on for untold eons;
These atoms contain lands unspeakably many,
And the atoms in these lands are even harder to tell of.

It also reminded me of a trap in an anime described as inescapable for conscious beings where they get trapped in their own mental dream states that accommodate to their infinite desires (kind of like a cosmic Matrix)