I just released an EP through CDbaby, so it's on all the typical sites, itunes, emusic, amazon, etc. I've had a few sales (and I mean a few), but I'd like to get out there more. The issue is, it's just me. Solo metal shows aren't exactly common. Plus, I'm in the military and stationed in Korea right now, so playing live is out. But, I have an EP out there, so that's good. I did a digital-only release - is that going to hurt me in the end? Do I need physical copies? They're just so damn expensive! So are there any ways to promote myself a bit without spamming everyone?
I have had the same problem. So I made a band. Well when myspace was around it was a little easier, but now that myspace is kind of out of style it's a little harder. Maybe buy a few ads on facebook, post your stuff to soundclick, and just put your music anywhere that it can be heard, maybe make a few videos on youtube.

Make some cool/different videos and use "video response" to videos and music that is similar to yours.

I'd stay away from buying ads on facebook, granted it's cheap, it's just not worth it IMO unless you have financial backing, there's better things to spend the money on.