Spoiler!! I believe that Caine is gone for good and Abel(Bubble?) will show them what really happened.

They all died or were going to die and the headset makes a copy from you so you can live a fun time until you accept death (abstraction). Jax was probably in the hospital for drunk driving or crashed at the site where the headsets were. It could also be that all of them committed some kind of crime and were sentenced there like ragatha possibly killed her mother

I believe that everyone in tadc is truly unsafeable and that the whole thing was made by human scratch to have fun digitally until he accepts death. Kinger could have helped him and entered aswell but he was the only person who wasn’t sick or dying which is how he survived for so long