It keeps getting better, and it looks like you're close to a finished still. But in case you still want pointers, I drew out some very basic guidelines on a screen of your first attempts, just to clarify what I was talking about in my post:
As you can see, when I talked about the jawline, I mostly meant the lower jaw muscles, where the angle of the jawbone is located. And the mouth can have the V-shape made less extreme and then pulled back a bit without loosing the overall "joker"-shape. If you look at your own mouth in the mirror and then grin, you'll notice that the corners of the mouth are drawn backwards as well as upwards, and even though the joker's mouth is deformed and extreme, it would still follow those same basic mechanics.
Also, you could define the ridge of the nose some more, and pull the nostrils back a bit. You have correctly translated the fact that nostrils flare and go upwards when grinning on your model, however, they do not go outwards very much. In your image the nostrils almost protrude more than the tip of the nose, which looks a bit off.
But again, these are just tips and pointers, and just in case you still feel you want them. I'm not trying to put your work down in any way, it's looking better and better for each screen.
Oh, and you nailed the hand. Very creepy and skeletal fingers.