These are very important questions which deserve to be addressed, and I hope this post isn't downvoted severely. However, at least one subset of them has been addressed already:

Further, although less dramatic, what if we succeed to transcendent, to become posthuman and find out that the universe does not contain enough fun for entities with mental attributes far exceeding those of baseline humanity? What if there isn't even enough fun for normal human beings to live up until an age of 150 and still have fun?

See the Fun Theory Sequence for discussion.