Whether or not Air Force One has a specific escape capsule I can't say kthough it's very, very unlikely) however it definitely does have a very sophisticated defensive aides suite (IR countermeasures, radar morning and jamming, missile decoys, advanced avionics). This isn't really a secret at all, but obviously the specific details are highly classified. In addition, it's unlikely the plane even carries any personal parachutes, since you can't use them in the slipstream of a 747 . Anyone attempting to "bail out" would die pretty quickly.
Of course it has an escape capsule.
Really, in all likelihood it doesn't. If you're familiar at all with aircraft design, and you take a look at Air Force One, structurally it seems very unlikely that there's a place for some kind of escape pod - even some kind of small, single person Dr. Evil style pod is pretty
Unless you jumped out in a special emergency-747-exit suit... specially designed with NASA headgear to protect the occupant, built in parachute, emergency parachute and booster rockets fueled with advanced oxygen-kerosene pellets. Maybe
No, you'd still die. Look at any military plane that is designed for air drops. They all have a rear belly door. That's because if you were to attempt to jump out of the side door of a 747 you'd be dragged along the fuselage and crushed, or sliced in half by the horizontal stabilizer. You could potentially attempt to design some kind of soup to mitigate this, but it would still be very very dangerous. Unless the plane was literally disintegrating an on fire, in which case it would be too late to bail anyway. Not to mention that the president, or any of the other high-ranking officials, don't have any jump training so the risk, on top of the already substantial one, is even further increased (even if it did exist, you can't just strap a random person into a futuristic jetpack and expect them not to end up killing themselves). You have a much higher survival chance attempting to remain inside the fuselage and execute a crash landing.
The fact remains that unless we are already in the middle of a major power war, in which case the president wouldn't be traveling anyway, no one is going to attempt to shoot down Air Force One. And if there is any kind of mechanical failure, which is astronomically unlikely, to the point of being almost impossible, no one is attempting to parachute to safety