Yep. When people say calories in nutrition, they usually mean "kcal".
Kinda like Mb != MB, cal != Cal, cal != kcal
Yes, but the body needs 2000-2500 kcal per day, not cal.
For all intents and purposes, when someone says cal they mean kcal. A single actual cal is so ridiculously small it might as well be irrelevant.
Yep. 2000 calories is 2.32 watt hours. 2000 Calories (kcal) is 2.32 kWh. That alone should be enough to clarify the difference, especially if you've ever manually turned a dynamo. Even after energy losses, a person can push a few watt hours into a battery with a hand crank in 10-15 minutes, drastically exceeding the energy output of 2000 calories.