You are pressuring the property too much. 320 acres is tiny and if there were possibly up to 20 sits before you even got a chance to hunt that place was ruined long before you got there. Especially when you have no idea if said person hunted when the wind was right (doubtful this year with the warm weather we've had and southern winds), spooked deer, etc.

Do an off season camera survey starting on the 11th. Throw some corn and deer pellets out and collect the cameras in three weeks. I bet you'll be surprised at how many deer are still around there.