I agree , very good shot and it looks like you are hooked.

This hobby will be very rewarding and frustrating at times but its a lot of fun.

One thing I can recommend to make focusing easier is a Bahtinov mask but thats just something I found early on.

From your post it sounds like you are converting to TIFF before running through DSS and it is better to send the Raw files straight through DSS.

The stars around the edge are out of round because of field rotation which is a result of bad polar align , the drift alignment should be for longer in minutes then the shot you are taking.