Hi Mike............ while much of this business is unknowable except via seat of the pant acquisition the internet has helped a lot........ Never before in written form you can now find excellent dissertations on every subject of interest to ourselves.
To begin: reset the search date on the browser for each subject to "show all of last year" and that will suitably bury you.
#1 "small second run" means you'll rarely get into the 90/10 as thios most applies to big, busy, sell out, packed theatres. In 7 years I've never had to deal with it. You'll pay minimum and flat fees vs. 35 or 30 % in a second run place. Older films, classics, are often the most expensive in terms of flat fee rentals. Also: shipping will chew you up on the classics.
#2 Too hard to project. Is the area scary? Near parking? Near a college? What's the demographics? A town of 20,000 should be able to support 2 theatres and maybe a sub-run such as you are suggesting. The problem is you'll be incredibly restricted by one screen!
#3 As population goes down..film gourmets go down. My experience was that there simply wasn't enough people to justify this type of programming in a for profit setting in a small town. If it was me I'd be booking 3-4 pictures and showing them on different times each day. I'd want more screens.
#4 Our 3 screen nets about 40 without paying my wife or I for the 80 hours per week we put in. Can it generate that on one screen? No, I don't believe so. However, if you have a college and or liberal area that loves film and just isn't being served there is a living to be made. I'd have to know your market before I answered that one.
Go out on a Monday night to the movies. Walk into each theatre and count how many are inside. Go Tuesday, etc, etc.
Get a part time job working at a local theatre.
Best of luck!