I took the TOEFL some weeks ago and I also guessed at least 2-3 questions in the listening section and I got a 29/30.
I'm sure if you get all the questions right in the real exam, you will get a 30.
To avoid distractions during the exam, I suggest you to use earplugs all the time, even during the Listening section. Then turn volume up to the limit and then you will only hear the conversations. In my exam I brought my own silicone earplugs and they saved my exam.
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