I empathize with your situation, I have had lots of presentations in college and at work and I've had many job interviews. The worst thing you can do is be unprepared, you should have a rap memorized and you should be able to recite it without thinking. It sounds like you did that but you also have to stay 100% focused on what you're saying. Listen to yourself as you speak. Focus on the words you're saying. I think what causes stuttering for me is my mind goes one way and my mouth goes the other way... so for example I'll be tying to answer a question about what my biggest weakness is and at the same time I'll be thinking about possible alternative answers,about the interviewer's facial expressions,about stuttering,about how nervous i am,etc... and that's what causes me to block. I have this technique i call "liquid mind" it's hard to explain but basically you need to shut off all parts of your brain unrelated to speaking. It's weird i can feel a physical shift in my head (probably psychosomatic) like right in my forehead and it feels almost like my eyes go crossed lol BUT I'm able to speak fluently when i do it. When I'm in that mode i don't see the person I'm speaking to, I look straight through them and I'm only listening to myself speak. I've used this for years I've had group mates in college come up to me after a presentation and say "who tf was that??" "what happened to your stutter?". Can anyone back me up on this? I've wanted to ask other stutterers about it for a while. I swear i feel a shift in my head like I'm flexing a muscle and it turns off unnecessary functions and I'm able to speak fluently. Not great in social situations, but for public speaking and interviews it's been my go to technique.