what freehand content refers to is the portion of the skin you could actually copyright, because you drew all of it. Tracing over the original skin and putting things in exactly the same place doesn't really count. Applying filters over the original skin, using the hue-saturation slider, or manipulating the original artwork in any way besides entirely re-doing it doesn't count.
The veins on the wings, bottom half of the legs, the bottom, side, and fin webbing on the tail, almost the entire horn, the bottom jaw, the front of the top jaw, neck, belly, back of the torso, and center of the inside of the mouth are all simple modifications of the original skin, which means no freehand. Which is probably more than 50%.
The nethery lightning effect you have on the horns is nice, the webbing on the wings is decent to. You just need to add a lot more touches like that to get your skin to an approvable state.