1) There's no specific way to fold a map the "military way" but I usually fold it so the part I'm using shows through the protective plastic sleeve so I can plot my points.
2) One "new" MRE provides approximately 1500 calories.
The "old" ones provide approximately 3000 calories. (They dropped the calorie count about 2 years ago. The original MREs were designed to supply a full day of calories for a combat soldier.)
So go by calorie count; one a day should work, if you're bringing supplements such as beef jerky, etc. ("gedunk" or "pogey bait") ,
as long as you're not hiking too strenuously.
It's more important to ration space for water, if you're in a low water area.