What is the ruling on one who experiences obsessive thoughts (waswasa) about divorce or its euphemisms, then doubts whether he uttered it or intended it, and subsequently acts contrary to what he had obsessive thoughts about, believing that doubt does not remove certainty?

No divorce results from the two phrases mentioned. What you are delving into will only complicate matters and increase obsessive thoughts. The cure for obsessive thoughts is to turn away from them and occupy your mind with reading the Quran, seeking refuge in Allah, and maintaining regular remembrance (dhikr).