You have the right idea. Mounting outside in the clear is going to produce better results. I suspect signal conditions will improve if you can consider using a push-up mast. If so, run a new report at 60' to see what signal conditions look like.
http://www.3starinc.com/telescoping_masts.html
A Winegard HD7698P equipped with an Antenna Direct CPA-19 would be able to receive signals down into the red highlighted section of your report.
With the addition of a rotator you would be able to fine tune aim of the weaker signals.
At first glance, you have access to ABC, CBS, NBC & PBS as well as several other 'newer' networks.
Are there trees in the area, if so, how tall and how dense?
How many TVs do you plan to connect and how long a run of coax would be needed to get from the antenna to the furthest TV?