Hi Grady.
The darkness around the edges seems to be a alignment issues. Basically you haven't been in exactly the same position with each exposure. So deep sky stacker aligns the bright objects and move the edges of each sub to do so.
The obvious answer is to try and find a solution to pin point your image subs, a lot easier said than done, i've found, although greater minds may enlighten us. Normally I just crop it out.
Without knowing what you actually did in processing, I downloaded your jpeg and had a little play, I hope you don't mind.
Now, I'm no expert but all I did was adjust curves, because we only have a pretty small jpeg to work with, you can't be do aggressive. I then adjust levels to bring the sky colour down and then performed a slight S curve to try and brighten a bit more of the neb.
These are only really basic things, but I've found that these are the most important,, if you get levels and curves wrong, well you just don't get there!
Have a look at this link
http://www.hyperstarimaging.com/video.php
They had some good tutorials.
Other then that here's my little edit and keep em coming and having fun.
Darren