1) The usual diagram of Neptune and Pluto's orbits is a "top down" view of the solar system, also called a polar view. In this view, the two orbits appear to cross. But this is a two-dimensional picture of a three-dimensional event! A "side" view shows that the orbits of Pluto and Neptune are also inclined to one another. In fact, Pluto's and Neptune's orbits never actually cross each other - at their closest, Pluto's orbit is "above" Neptune's by a few hundred million miles. This is like the difference between looking at a road map showing that two roads cross, but then driving to the "intersection" only to find out that one road is an overpass and you cannot actually get from one road to another.

2) The orbits of Pluto and Neptune around the Sun are in resonance. This means that every time Neptune orbits the Sun twice, Pluto goes around exactly three times. When one of them is near the "crossing point" (remember, they don't actually cross) the other one is somewhere else entirely on its orbit. The inclination of Pluto's orbit is not entirely stable - over time it will change and this might eventually cause a true crossing with the orbit of Neptune. But the resonance, which is extremely stable, will prevent the two of them from ever being in the same neighborhood at the same time.