You just need to change the parameters for the argument, nothing else.
<string>n_abydon_arguments_won</string> <string>EqualTo</string> <string>3</string> <------This needs to be changed to 3
Don't bother doing anything else. It tells the game that you won 3 of the arguments needed to unlock the dialogue choice. I did it right before using the crystal, after talking with them for a bit and winning 1 argument normally, the option appeared. Just tested this and it worked fine for me.