I used a play call sheet back in the day. I unfortunately lost the file and can't remember much. I do know I had sections for 3rd & short, 3rd & long, red zone, goal line, backed up offense. Basic situational football ideas that I picked up from reading the following link:
http://smartfootball.blogspot.com/2007/08/bill-walsh-method-for-game-planning.html
1. I always scripted my first 10-15 plays (can't remember if it was 10 or 15). My script was designed to establish my bread and butter, see what kind of looks I get from the defense, and to set up my constraint plays. How do they look against our base run to the left? To the right? How do they align against trips? Stuff like that. Just trying to answer questions you may have while setting the defense up. The key though was the situational play calls. 3rd and short? Go to the 3rd and short section, pick up the first down, and then back to the script. Time to call your 8th play on the script but you got pinned on the 4 yard line by a punt? Go to the backed up offense section. All those ideas got me through the script so I would have a good sense of what's working, what's not working, and what constraints I've set up to catch the defense off guard.
2. I can't remember exactly how I had my play call sheet setup, but I built it on Excel and then printed it out so it was next to me while playing. It may have even been double sided, but I can't remember. I made the fonts pretty small, created boxes and sections, used color coordination. I basically just set it up in a way that made sense in my head so I can think of the concept I want, and then get it. I attached a spreadsheet that I did manage to not delete. It helped me think of a concept, and then quickly pick the call. You'll see that I had my formations going from 1 back under-center, to 2 back under-center, to shotgun. Like I've said numerous times, I do not have the play call sheet with the situational plays and such.
3. Not sure what you meant with your question. Let me know if I did not answer it.
4. Definitely. For example, my base ground game could be utilized on 3rd and short obviously. Unfortunately, I can't remember if I structured my spreadsheet to indicate that. I imagine I probably would have included them as 3rd & short runs.
5. I did this several times playing in the BSCFL back in the day. I would write down my 10-15 play script depending on the factors above, as well as the long-term psychology of playing an opponent multiple times. It's really a mental game of cat and mouse that could go on and on. For example, suppose you have an opponent that knows you are a run first kind of guy. Well, you're going to want to establish your running plays so you sprinkle them into the script. Play 1 could be a run, play 4, play 9-11, whatever. Problem though is this guy knows we want to run the football. Solution? Change things up a bit. Maybe you develop a script to throw more than run. Maybe you feature play action early, although I feel that it's best to set up play action. Each game's script was unique. From there I would just stick the script and call upon my situational plays.