It's perhaps worthwhile pointing out that even as there is nothing to compel you to accept notions such as "cosmic significance" or "only egotism exists", by symmetry, there is also nothing to compel you to reject those notions (except for your actual values of course). So it really comes down to your values. For most humans, the concerns you have expressed are probably confusions, as we pretty much share the same values, and we also share the same cognitive flaws which let us elevate what should be mundane facts about the universe to something acquiring moral force.

Also, it's worth pointing out that there is no need for your values to be "logically consistent". You use logic to figure out how to go about the world satisfying your values, and unless your values specify a need for a logically consistent value system, there is no need to logically systematize your values.