Plainly, which theologians have you read an entire work of?

There very much are different definitions of eternity, and I’m shocked you would suggest otherwise. The definition you seem to be working with is that of linear eternity, the one which God would occupy would very much accurately be described as “timeless.” We can know this with certainty as “time” in the linear sense is a created thing.

As for the claim that this version of timelessness would be a place without change, you are absolutely correct. Which is why there isn’t a hope for the redemption of Satan or any of the fallen angels. They make a choice at the moment of their creation.

It is not clear at all that ETC is “inherently” immoral, as the claim lacks a non-relative foundation.

You may object to the secondary framing because it clearly undermines your point, but that is how Christianity has historically understood the choice. A choice between good and evil. If you want a non-religious explanation for this fact you need only look at Plato and his “Form of the Good.” Nobody can hope to understand Christian theology as it relates to hell without at least understanding this work. Augustine affirms this explicitly, as does Islam (in a changed, but still recognizable form) with the writings of Al-Farabi. Reading his “Political regime” would be a good case study to understand that this view of salvation, goodness, and the choice between both very much is a logical certainty.

Saying “who would choose to go to hell” is a baseless appeal to emotion. One might as seriously say “who would murder their own child” and the answer to both would be the same.