Many of those proficient in Morse might be stumped when it comes to sending @ or %, fortunately the ITU-R recommendation on International Morse Code provides an answer.
The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communication.
Recommendation ITU-R M.1677-1 (10/2009) confirms the International Morse code characters and the operational provisions applying to their use in radiocommunication services.
The Morse code for @ is .– – .– .
For the percentage sign % there is no corresponding signal in the Morse code and they recommend that the figure 0, the fraction bar and the figure 0 shall be transmitted successively.
A whole number, a fractional number, or a fraction, followed by a % sign, shall be transmitted by joining up the whole number, the fraction number, or the fraction to the % by a single hyphen.
For 2% you would transmit 2-0/0
The ITU-R International Morse Code Recommendation M.1677-1 (10/2009) can be downloaded in Word or PDF format - http://www.itu.int/rec/R-REC-M.1677-1-200910-I/en
Other ITU-R M Series Recommendations are available at http://www.itu.int/rec/R-REC-M/en