Quite an array of images, for a beginner you have really leaped ahead, the unmodded camera will make the red hydrogen emissions a challenge, but you've shown you're up for it.
As for advice, probably one of the most common errors made is how stars are handled, they need to look natural after you have lifted the rest of the image be it a nebula a galaxy or whatever.
Careful with sharpening as it makes the edges of the stars hard (crunchy) masking can help here, even by duplicating prior to sharpening then using the selector tool to restore stars from a non sharpened image into the now sharpened one.... The minimum filter can also help bloated stars but needs. To be used selectively on the bigger stars not just across the whole image.
Practice, practice and practice will see you corner all the techniques.
You're certainly on the right track I look forward to more.
Thank you very much for the nice feedback.
