I HIGHLY recommend you get rid of the video just before bed. Studies have shown TV and video games keep children's brains stimulated for several hours, so that could definitely make it harder for your child to relax and fall asleep.
What works best differs from child to child. With our son, we go through the routine and simply leave, and have always done it that way. For him that works, and sometimes it's the only way to go. Since your son is already used to falling asleep with you right there, what might work better than trying to leave sooner is to start further away. Instead of sitting on or right next to a bed, spend a week sitting a couple feet away. Then keep moving the chair back until it's in the doorway. Finally, move it outside the door. Then you can work on closing the door until he's used to you walking out and closing the door behind you. Good luck!