Here is some ideas:
"e" should be a dit, not a dah, yes?
In Morse code the length of a dah is usually three times a dit, I believe.
I would use three values for the dit and dah values: 1 = dit, 3 = dah, and 0 = no blink. The need for the third value is to allow you to pad the unused array elements with a value since some only use one like "e", while others like "1" use five
Use a two-dimensional array and initialize the second element with your dit and dah data. The offset into the first element of the array can be the character's ASCII value. Thus, if you have an int array named didah, then didah[65] = "1","3","0","0","0" which represents "A" (ascii 65) and would return dit dah 0 0 0
You could then use a function that is passed the value from each of the values in didah[65]. The value could then be multiplied by 500 to achieve the delay time.
I'm sure you get the idea...
read a character from the Serial object
convert character to ASCII and store in a variable
then pass the variable into a function that enters a for/loop to read each of the elements at that offset and passes the array value to your blink function
the blink function turns ON the LED for 500 * the number milliseconds -- 1/2 second for a dit, 1.5 seconds for a dah, and 0 seconds for the padding
don't forget the pause between letters
I hope I've been clear.
Good luck, and ask if you have further question.