(1) From the statistical chart of broken lines, it can be concluded that Xiao Ming spent a total of 140 points from his departure to his return home.

(2) As can be seen from the figure, it takes 140- 120=20 minutes = 13 hours, 5 ÷13 = 5× 3 =15 (km/h) to return.

(3) According to the statistics of the dotted line, Xiao Ming walked 2 kilometers from home in 20 minutes, stayed for 20 minutes, and then moved on. Twenty minutes later, he drove three kilometers to the library, borrowed books from the library for 60 minutes, and then returned home in 20 minutes.

So the answers are: (1) 140, (2) 15.