When you AP you retain some connection with your body. When you are Aping though it can be cut and then you can be very vulnerable. Thats why it is important to keep up some defence on your physical body and astral body. If people are trying to cut the link you can get your body back by a quick inhale and try to envision your astral body comming quickly into your physical body. Take care and keep defences up.
also a good tip is to remember your "Evil be gone" astral powder!
if something is acting you throw it directly in their eyes and run. If they keep coming back put on ur boots and kick em in the face, if they grab you shoe, then do a spin kick that knocks them away and run to your body and do a protection spell
possible, but never heard of any cases. if you are worried, cast a circle. there is always some part of your contiousness left behind so if your body is in any type of dangers [physical or spiritual] you're instantly zapped back. any fear will provent you from projecting, you don't need to worry, nothing will happen. if you feel safer, cast a circle, shield, wear a protection charm, something like that will protect you.