How and why values are subjective and objective for existentialists?

Existentialists = a philosopher who emphasizes freedom of choice and personal responsibility but who regards human existence in a hostile universe as unexplainable (Wordnet)

Subjective = taking place within the mind and modified by individual bias

Objective = belonging to immediate experience of actual things or events

Personal responsibility and the degree of it is subjective and objective as a person will always decide at some point that *something* exists outside his/her realm of responsibility. As they believe in a hostile universe, there is no reason to act for the good of anyone else in a case like that or step out of their limit of responsibility. For all they know, that step could go against them.

And as we all know, freedom of choice is subjective. What do we mean by it? Freedom of choice in stealing cars? Or freedom of choice in which dog steak to buy at that road-side stall? The interpretation depends on the person.

The key in understanding why no two existentialists' values will be the same is in the last part of that definition courtesy of Wordnet: "human existence in a hostile universe as unexplainable". Law and authority are chaotic. The individual suffers under the system. There is only the certainty of death. The sufficiently motivated E-list (I got tired of typing that Word, sorry) may attempt to seek out meaning for life anyway - it's one of those innate human needs. And because they have nothing to go by - just the atheistic, philosophic mindset - who knows how they will interpret the situations they come across in life to create or cross-out the whys of existence?

IN short: what has the existentialist to go by?