The 3d model is a "Frankenstein" of different free 3d assets. The animation is done by me, yes.
Here how I made it if you're interested: https://twitter.com/dene_pixelhands/status/967432494504136704
Seems very PJ worthy to me, excellent work !
Reminds me of the graphic novel "Maus".
I think it should be allowed since you didn't hide the fact that you used 3D ref and have clearly cleaned up the frames. Some frames have minor jaggies and using the colours you have you could have done some AA but that's just nit-picking. Did you make the model and animation yourself? They are both very good.
the animation feels a bit weird on how long the recoil is, one would expect with the pose to come a really fast recoil, but maybe the bullet's stronger?
anyways i think this should be approved anyway cause there's no way to get such a unjagged outline without additional work, counts for me 
This looks rotoscoped! Great job! Moves great!