[Jatd]

I don't know the answer to your question but your story was very interesting non-the-less and I appreciate you sharing.

Did you ever figure out where the big hand print came from? What did your mom make of it? ... and what did she make of the light she saw in the bedroom before his heart attack? Does she ever speak of it?

As for the selling your soul to the devil, I think thats more about selling your soul to the world, greed, selfishness, the need for power - none of those things are fulfilling and will ever bring happiness, only a temporary false happiness and then one will be left in their own hell due to their greed and selfishness.
It doesn't sound like your dad was those things.