I just had ... a thought. Could it be that ... Lord Jack, Union Jack, whatever ... became the host for LEs souls after he destroyed the Lil Cal in his prison cell? That would explain why big green LE stopped working after Lord Jack was killed.

The Lil Cal in the prison cell is the Exit, not the Entry, the actual Lil Cal with LE’s Soul is out in the Furthest Ring, and through those eyes he pretty much possessed Union Jack to become yet another iteration of LE (Do remember that Lord English has countless iterations of himself in the Multiverse). When LE ‘stopped working’, Jack was already dead, so judging by the green flickering aura fading away before the eyes lock onto 8-Balls, it’s more the Collapse of the Green Sun that froze him. That and the fact he was predestined to end there in a way.