First, the warranty issue. Original bumper to bumper warranty is 36 months, 36,000 miles. The degradation warranty for the main battery pack is 60/60k. The battery defect warranty (not likely to apply) is 96/100k. Due to their age, the degradation warranty is the only one to worry about at this time. As long as the car does not have a salvage title, the original warranties apply to any owner of the vehicle.
Most dealers are not concerned with the use of Leaf Spy. If they are, you probably don't want to deal with them. Leaf Spy tells you a lot about the health of the battery, but the output is not officially recognized by Nissan as being useful for anything. The numbers to be concerned with are AHr, SOH, and Hx. The higher the numbers, the better. Get a CarFax, or something that shows where the car has spent its life. Avoid anything has has been in a warmer, or hot, climate (Florida, Arizona, Nevada, etc.). This is a big factor affecting the life of the main battery.
Don't let the removal of the 80% charge option sway you. It is okay to charge to 100% every time. In fact, it needs done on a regular basis to balance the cells in the main battery pack. What is not okay is to let the battery sit at 100% charge (or below 20%) for extended periods of time, especially in hot weather. What works well, for many, is to use the charge timer so the car is ready to go within an hour or two of departure. As long as the commute gets the charge level down near 80% (or below), sitting at work all day should not be an issue.
2013 Leaf SV - Cayenne Red - QC Port - LED Headlights