Hello Lauren! Well, the equivalent of "go too far" in Spanish is "ir demasiado lejos", this expresion is very common and you can use it the same way you do in English: "Esta obsessión ha ido demasiado lejos/This obssesion has gone too far". Now, if i'm right, "idiom" in English is a phrase that has a figurative meaning, so the word in Spanish would be "modismo". But if you are asking for the word "idioma", the meaning is different because this is only a synonym of "lengua" in English "language". I hope this helps.

La respuesta depende, ya que depende de la situación supongo. too far gone sería algo como "has ido demasiado lejos", referente a you go too far gone with that joke. Y sobre "idiom", su equivalente sería idioma. Y "language" es lenguaje. Idioma y lenguaje sería lo mismo, puede usarse cualquiera de las dos.