We are all lucky to have such a forum that you could receive the quality answers given above (well, maybe not mugwumpjism's drug propaganda). Allow me to submit a more holistic viewpoint. You say that you seek new intellectual challenges. A fine path. Your post also seems to suggest what you seek is, perhaps, value.

Pushing bits and editting .conf files can become a bit pedestrian, no? So you seek a way to push bits that has a more substantial purpose? Again, a fine path.

Return to college, please. The degree you receive is the least valuable thing you will get there. Find a nice large institution where you may dabble in all aspects of science. And art, literature, music, etc. I submit that you do not know how much you do not know.

You will change careers many times in your life. That shouldn't frighten you. What should frighten you is choosing a career because it has been "sold" to you by the media.

A final suggestion. What are you worst at? Painting? Speaking? What have you never tried? Try it.