Explaining how to "read" sign through a keyboard, would be extremely difficult. Being able to track & read sign comes mostly from experience.
One thing that will help determine the population, next time you're scouting, break your coon tracks down into 2 or 3 size groups. Once you know coon tracks it's fairly easy to tell the difference between a "small" an "average" or a "jumbo" track. Again, identifing "fresh" tracks comes from experience. Nice crisp tracks, sharp edges, being able to see toenail marks in the track, etc. are all good indicators of a fresh track.
Same with the scat piles, tear them apart, see what it's been eating.
You've still got 23 miles of creek to scout, I'd park my vehicle someplace and have someone take me up the river 4 or 5 miles and drop me off. You'll learn more on the walk back to your truck than we can tell you in a week, with our computers.