Being able to jump and also benching a certain amount of weight isn't fitness either, though. Both are anaerobic exercise. I would argue that you are probably of above average fitness aerobically, but at average or below anaerobically. I doubt many people who can run in races are necessarily good a benching. In fact, most of the people I remember from school who were in track and field were pretty weak, yet were extremely physically fit. I also know people who go to the gym all the time and work on muscle tone who couldn't run a couple of blocks. I guess I'm trying to differentiate between aerobic heart fitness and anaerobic strength fitness here. Most people have weaker aerobic fitness.
Yep. Have you seen Olympian distance runners? They look anorexic. But it makes sense. Less muscle mass using up less oxygen in the bloodstream so as to more easily sustain aerobic activity for longer periods of time. The body optimizes itself for the activities we train it to. The style of training I prefer is High Intensity Interval Training (HIIT). It's a decent enough cardio workout that simultaneously builds muscle mass, packed into a fairly short amount of time. Kinda like crossfit, minus the stupid.