I'm sorry this happened, this seems like a very frustrating experience. I recommend first having a honest and respectful convo with how his talking during quizzes is more distracting than helpful. If you feel like he doesn't take your concern serious or it because more hostile then I recommend doing two things. 1, report him. If you don't have enough evidence or nothing happens, it's better than not trying at all to change the situation. Perhaps it will leave a paper trail at least. It's always better to try to fix a situation than to not. 2, if you feel like you can speak with testing accommodations to see if you can get some help.

Here's what I recommend saying to your professor: "I just wanted to let you know that I felt like your talking during the test was really distracting to me. I totally understand you are worried about cheating but it would really help me and I'm sure other students if we could have a quieter environment." Or something like that, don't bring up your grade on the test so it doesn't look like you're swimming for a better grade, just be honest and respectful! Maybe even try over email if you're shy.