Have I committed an act of disbelief (kufr) or polytheism (shirk) by uttering offensive words that were said in front of me, or by relaying them to others out of anger, especially with an obsessive-compulsive disorder that makes me doubt the reality of what I uttered?

Disbelief is not incurred by any of the things you mentioned, so completely turn away from thinking about these whisperings (waswas); your dislike of them is proof of the soundness of your faith. Strive to rid yourself of them, for you will be rewarded for that. Learn Tawhid (monotheism), for it is a protection against error, and always recite the supplication: "O Allah, I seek refuge in You from associating anything with You knowingly, and I seek Your forgiveness for what I do not know."