You right now exist on a planet with an epic amount of empty space: deserts, oceans, and a ton of 3D volume under the ocean surfaces. You can spread out today, right now. You'll have air available for free, at a pressure and temperature you can tolerate (or easily modify to get there).
Space isn't going to improve your nihilism. It's incredibly hostile to life, and you'll put in all of your effort just keeping from asphyxiation. The rocks out there are different from earth rocks, but I bet you haven't even put much thought into all of the different kinds of rocks you have available to you right now.
I suspect you'll quickly get bored of the fact that non-living planets have a lot less going on than living ones. There will be a chance for people to do them the first time, but the low-hanging fruit will all be picked quickly, and everybody else is just going to be standing about wondering why they wanted so badly to go to a place with nothing interesting happening.
Don't get me wrong: space is cool and I'm glad we're going. But I don't think it's the existential cure-all that you (and many others) seem to imagine that it is. If your actual interest was spreading out, you'd already do it. I believe that your malaise is due to something else entirely, and I think you could take more realistic steps to do something about it.