Hi Kaz!
Congrats my friend, you are simply nailing it!
even though you are at the process stage, I want to give you some little tips, if I may
I manipulate your picture with photoshop, here it goes!
- The eyes are slightly small, and the sclera or white too, Lincoln had very asymmetric eyes and his iris were not line up.
- the eyebrows should be darker, will increase the look expresion.
- the beard, is a kinda transparent in the center and not completely straight, also darker will look better with a few grey hairs!
- The lips, the upper lip should be more angular and not curvy, some more reflection will look better.
-maybe the light on the tip of the nose could be as I draw in PS, not sure how to describe that lol, also reinforce the wrinkle on the top of the nose!
hope this helps my friend, looking awesome cheers!