Andy,
When the course opened for play, the idea was to provide a place where Worthington and his friends could enjoy themselves ona good and challenging course. At 6,011 yards it was everything that they needed. During that year, and leading on into 1912, Worthington decided that he wanted to sponsor an "Open" tournament and offer considerable prize money to the professionals who would play. He believed that they deserved it and that it would certainly boost exposure to the Inn and golf course. His problem was that the course as it was, fine for himself and his friends, wasn't the superior challenge that he wanted for the best players. So Tilly did a complete redesign and re-routing adding about 500 yards in length.
This course received absolutely rave reviews and the Shawnee Open attracted the best players in the world in 1913 and onward. Players such as Vardon, Ray, Hagen, McDermott, Fred McLeod, Alex Smith and his brother and many, many others. Most are actually unaware that Sam Snead was the playing professional for Shawnee in the late 1930's, well before he would do so for that second-rate resort in Virginia...
To asnwer your questions, no, the current range does not run down the path of the original 18th hole. Go back and take a careful look at the road leading to the front entrance of the Inn and where it runs to. It begins at the END of the street that Worthington Hall is on, and so the 18th hole ran parallel to the Delaware. Actually, portions of both the original 16th and 17th holes cross over what is now the driving range, Doak's Tillinghast challenge course and the Tillinghast Academy grounds.
The original 18th green PROBABLY was used for the new green for the practice hole. But I believe that it was changed to reflect the direction of the shots being hit into it.