You're not crazy.

Demons aren't going to take over your body.

You won't go to Hell.

There are several layers to the mind. While we're awake, the gross mind is manifest. Basically you're brain is taking in the information from the world around you and your gross mind is perceiving and identifying those phenomena. Think of it as your gross mind being the flow of thoughts. Basically it's the central processor and your brain is the hard drive.

When you fall asleep, progressively more subtle minds become manifest. While dreaming, our subtle mind is manifest and it has disconnected from our gross body. (You're perceiving your dreams instead of your body.)

Here comes the really icky part.

For someone who has suffered strong trauma, their mind "grasps" more strongly than most people. (Key word "most", not everyone has to have endured strong suffering to experience this.) As you sleep, your mind doesn't want to let go of it's gross connections so though your subtle mind has become manifest, it's still clinging to your gross body and the world around you. It's a sticky, messy little phenomena I called grasping above.

So what happened was your subtle mind was beginning to manifest and trying to perceive your "dream world" but since your mind was grasping at the gross world, you "fell out of bed" and saw what you saw. It's not a figment of your imagination. It's very real and a good sign that you floated, drifted instead of plummeting (and some people would argue that it's a very, very ... very good sign).

The demon phobia is an imprint, a cootie, left over. A negative impression and something we all have. Since your subtle mind began to manifest, those imprints were still affecting you later leading your gross mind to freak out and cause your panic attack.

Long story short, what you experienced was no less real than anything else. Enjoy it if it happens again and don't worry, you'll be perfectly safe though the whole thing.