I got past 500 on my first try. Right as I was getting bored, the big asteroids started coming and I noticed the orange speed upgrades are permanent. I had fun! It's pretty cool that this was done with such a low resolution.
My understanding is that the meter on the left shows how much space is between your ship and the enemy fighter trying to destroy you. I was a little confused about why sometimes I seemed to be going so fast and it was still gaining on me, and other times I was going slower and it seemed to be backing off. Increasing my ship's speed also seemed to affect asteroid velocity in a non-intuitive way. None of these things are really issues considering that this is a low-rez arcade game -- I didn't expect any hand-holding and I think you've done a good job of providing cues for players to figure things out (eventually).
Kudos on finishing, and thank you for sharing Space Disgrace with us!