Finish well and the stumble won't be remembered. You won't have to go into the Witness Protection Program. Most people are more concerned with their own lives to devote that much energy to you. A room full of people wearing funny hats, now that's a terrifying image. Relaxation in front of an audience comes from confidence.
Confidence comes from planning, practice and perseverence.
No, it's not the grade, that is the result from achieving your goal, which is dependent on your assignment. You first have to keep the audience listening. Don't use fancy jargon you got out of an article just to impress them. It won't work. They'll stop listening.