I much prefer your new renders, I like the fact you have used reds and greens and yet avoided looking christmassy. I think I understand the nostalgic look your after and hopefully I can give you some tips, to help soften it.
Normally I wouldn't recommend changing your reference 3 times :) but I think that you have come up with something much more unique for your showreel. I hope that you are happier with the end result. It is much more endearing than what you started with.
The direction of your key light is not immediately obvious. You will not see a shadow that faint and that sharp in the real world. Faint shadows tend to be soft occlusion type shadows rather than the key light shadows. I like to think of the fill light as the base lighting, you add the key light on top to add depth to the image. If you do have shadows but can't see them, it's because your fill light is too overpowering, and your key light is not intense enough. This is a common mistake by lighting beginners, possibly because students automatically think that lighting is about being able to see everything and therefore make all the lights the same intensities. The result is flat looking CG images. If your not sure what a light is doing, or where a particular light is coming from, look at it in isolation. Black patches where there is no fill and no key light look ugly, perhaps use an ambient light to bring up the black spots, re-place your existing lights (or re-think the type of light) or add an extra light (perhaps a subtle bounce light).
Observe my quick renders and comp (ignore the shadow direction, this is inherited from someone else's post).
The key light adds the drama, the more contrast there is with the fill light, the more depth your image will have. As you have a flat background you have no other way of getting depth into your image other than with lighting. I have used a greener blue for the fill and a orangey yellow for the key. The blue is a warmer blue, combined with warm key, the overall impression is of warmth and softness. The strong key light also directs the eye to your subject, see the reference again for inspiration.
I took old reference, most of it over 100 years old, because although computer lighting is a relatively new subject, the concepts and traditions we use are very old and well established. There is no point trying to do something new, until you have studied the past. I recently went to the Banksy exhibition at the Bristol Museum near where I live. My favourite piece is a big stone with some words engraved on it. "The bad artists imitate, the great artist steal." below it, Pablo Picasso is crossed out, and Banksy is inscribed :)
The only way you can literally soften an image is by either softening the edges, which would only look right if your objects are moving (motion blur) or depth blur (and you have no depth), or by softening something in the images, ideally the shadows. It only needs a tiny amount of shadow blur to soften the whole image, see the image below where MR shadow blur is set at 0.002. Also make sure you use your occlusion pass to get those realistic soft occlusion contact shadows. This will help bring the whole thing together.
I personally wouldn't use an incidence shader as a rim light, but it does a good job of making the character stand out from the background. I would try to keep it a little more subtle, and perhaps tinted a cooler colour to contrast with your warmer key light.
Don't feel that you need to have a central composition, I think it is more interesting slightly off center. You will need the stronger lighting to direct the eye, and then add a vignette to frame the image. As a final note, re-read the other posts, ones to Lies and Holly, as well as the shadow extract, should be particularly useful to you.
Good Luck finishing off, I hope have time to make some changes before the final deadline.