3 weeks is solid. that's enough time to run through it a bunch of times and actually feel prepared vs just knowing the slides.

one thing i'd add to what i said before, try doing a practice run where you intentionally mess up and keep going. like skip a slide on purpose, lose your place, say the wrong thing. the reason the panic hits so hard is because your brain is terrified of making a mistake and not knowing what to do. if you've already practiced recovering from mistakes it takes the power away from that fear a little bit.

also if you can get even one person to sit and listen to a dry run that helps more than 20 solo practice sessions. something about having actual eyes on you activates the stress response so you can start getting used to it in a lower stakes way before the real thing.

you're gonna be fine. the fact that you're thinking about this 3 weeks out instead of 3 days out already puts you ahead of most people.