The second ending, which I'll call the "Empty Symbol Ending" I got after doing all H-scenes with Mal0 and taking Si-Won's offer. When Zellen first appeared, I had her caged first and never freed Mal0 either time.
I mean, the endings are as follows:
The cheese steak ending: Refuse to give up malO at the last moment.
Box malO: Keep malO in the box.
Death?: Do what malO asks at the last moment. fredi fazber.
Death: Do things that get you killed near the end of the game.
My opinion on the symbol is as follows: Taking nothing to mean the world "lives", X to mean the world "dies", and / to mean "uncertainty".
The last one is more iffy, but it could refer to you being "inside" malO? In more ways than one.
I don't think chapters 1 or 2 actually pertain at all to the ending.