How long is a screenplay that is three and a half hours in page length???

I think two hours is long enough to tell any story. Because anything longer than that is going to bore the audience, and they will begin to walk out of the theater. You gave up too much information about this project, someone else with better contacts could crank out a script and get to wil smith before you do, so just be careful about giving details. God Bless you with your story, and I hope to see it on the screen.