Subdiv algorithms don’t play nice with N-gons. You need to make sure your mesh is all quads to start with. I think this is the source of most of your issues.
Also, don’t be afraid to look at other people’s work for technical inspiration. Go on turbosquid, and look at revolvers. You don’t have to buy anything, just look at the images. Find a bunch that look good and look at the wireframe pictures. Get an idea of how big the polygons are for the details you want, and how they’re laid out. Find the things that look good and use that in your own work.