Nice Cabbage!
In the end I had to burn a copy of Last Alert so you might as well. My original I own was bought for $4 back in 93. There are not a ton of scratches but one looks pretty bad. I get boss music and cut scene sounds, but no game level music or map music. So, I just played a burn with no issues. I'll get the disc resurfaced at some point.
I know you can continue, but I'm trying to 1CC. I haven't played in a few days, but I can at least get to level 7 on one run. I have this weekend so will give another few runs. It is a great game to come back to after a long hiatus.