1. The brackets are the indicator that this is a keystroke. You would not need to include them -- just use the symbols for keystroke and termination. A note on the TN page could notify the reader that the keystrokes are enclosed in brackets in print.
2. If you look at example (7) in the keystroke update to the Nemeth Code (2007) you will see a similar situation, except the arrowheads are one above the other. A short shaft is used in that example. A multipurpose indicator is required between the two arrows to indicate that they are printed horizontally and not vertically. §149