Thanks Alfsici! I have made a few creative changes to the saber tooth, including extending the Metatarsal Bones a bit larger for a bit more spring in the animation. However you are absolutely right with the length and size of the Femur. I'll give an mid weekday update on the update of the rig In the image below is the leg setup i'm planning to replace with back leg with. I think it would be a step towards the right direction in being more proportional.
As for the strait spine, I'm not sure if this is a good practice but I have a habit of making strait spines. It makes it so that the inherent mesh deformation of object is a lot easier to handle.
In addition to the update i have started working on animating the saber-tooth. I took reference from a cat run-cycle and placed it with the proportions of the skeleton. (animation is very rough, and timing has not been implemented yet)
Critiques are always welcome and thanks a ton for helping me out! I'll try to fully finish the rig by the end of this week, in addition have the animation timing implemented.