I think hypnic jerk is just one swift jerk of mostly your legs, but could be whole body. This is associated with process of falling asleep.

The falling sensations - like you falling through your mattress, lasts longer than the hypnic jerk and I believe happens just before you enter a dream.

When we dream, our heart rate goes up naturally, and also heart chakra gets more active (at least, that's what I have heard).

Maybe you were not before REM, that's why you didn't enter a dream. But everything else sounds right, just keep trying. Happy dreams