Translated text is in others/translate/assets/RJ162718.json. The [p] is for how to in-game display the dialog, like: [p] waits until you click and displays new dialog, so it's usually at the end of it, [r] splits the text to the next line, [lr] waits until you click and splits the text to the next line. [p_name] is replaced in the game with the name of the penis you set but in this form "[p_name]" is used in game version 3.0.22 in 4.0.6 it is changed to something like this "[Hxns n=p ex=1]" so I assume it's just a translation mistake but it shouldn't mess up the game, Sylvie just won't say "penis" in this text.
As for the name change and text box you have to play around a bit to get those options to appear, if you already have them try changing your name to for example "Rock" if under "refer to me as" is Rock and Sylvie calls you that then it works, in the text box you can't type just anything, it has to be specific words or sentences but it looks like they aren't translated, type "料理" if Sylvie answers then it works.