Most of the comments above are spot on, the OOF line needs to go as does the extra nut/shell on the floor as that indicates baiting and distracts from the image. Remember with wildlife we are always aiming for the most natural picture to fool us of where the critter was photographed.
Also, I know we harp on about it time and again, the focus on the eye really does need to be spot on, as you have not applied any sharpening to this shot yet then that will be easy to recover and correct but it is noticiable that the focus point in on the squirrels shoulder.
Comparred to your first efforts at squirrels and bearing in mind that this is from all new equipment that you openly admit you are still learning the above shot shows how far you have come along is such a short time. Don't get into the mind set that you don't want to post process a picture in PS though, you owe it to the shot and yourself that you bring out the best in any picture that you take.
You wouldn't not use some of your equipment just because some may consider it giving you an advantage, so don't discount every software tool that is available.
I look forward to seeing the finished shot
