Abbreviations used in federal tract books

I'm new to Federal Tract Books and am baffled by some notations:

1. The abbreviation "Dr." appears before some but not all of names of purchasers/applicants.  It is even printed on the book pages.

The page* below contains names preceded by Dr. (underlined by a solid line) and names without titles (underlined by a dashed line) [in order of appearance]: 
Dr. William Ballew, Moses Cloud, Francis W. Hamilton, Dr. Patrick Woods, Francis W. Hamilton, Dr. William Lewis, Dr. Matthew Russel. 
Francis W. Hamilton appear twice, neither time with the prefix "Dr." 

Is there a distinction being made? 

2. What is the meaning of "Located by name"? (Box "Aaron Stout" in image below) 

"Located by" appears infrequently.  I suspect this does not refer to the surveyor as I saw one instance where a Mrs. somebody located the land.

Any help would be appreciated.

*Federal Tract Book Terr Haute, Indiana Vol 1, p. 133