Yes your sigs are very monotone (Mono for one, tone). It seems like you're trying to make the brushing more of a focus then the actual image.

Blending the render doesn't mean lowering the opacity and erasing tips of the edges. In fact, you shouldn't do that at all. Brush around the edges to blend it in.

I'm not much for using brushes, as well as sig making so I can't give you much advice here. But just keep at it, you've progressed more then you think in the last few weeks.