OK, need to hide away from the awful awful news, so will distract myself here, and hope I can help you. Helping someone might make me feel better about living in a country with 52% xenophobes ... Let's hope we have a university system left in 10 years' time.
Yes you are likely to meet the other candidates. I've made some good friends in rounds of job interviews - think of it as an opportunity to develop networks of potential colleagues.
And from the other side of the selection process (I've appointed many many people) in the Humanities: while we don't judge your behaviour outside of the formal selection procedures, we will be observing to see how collegial you are. Universities are high-pressure, high-stress environments where we only survive through working as teams, and being there to support each other. We'll be looking at how you might contribute in this way.
You don't need to wear a suit - although the men in my field often do for their interview. A smart dress + jacket, or trousers/skirt + jacket, or even no jacket, will be fine. Be comfortable but not sloppy.
But if you're going to have to do something practical - a demonstration, a bit of physical practice of any sort (manipulating a patient etc), then dress appropriately - make sure that if you take of jacket you can work in shirt sleeves etc. Or ask about changing facilities.
Use waiting time to look at the facilities: library, art gallery, whatever is relevant. Ask for directions to the library or labs, or studios, or working spaces. Show you're professional, by wanting to see what tools you will be working with in lecture theatres, or demonstration labs etc.
If it's a 20 minute presentation, do it anew. Don't try to "shrink" a 50 minute lecture into 20 minutes. You'll be speaking to potential colleagues, and showing them how and what you teach. Use it as an opportunity to show the power of your content (your professional knowledge) and the efficacy of your method - your teaching style. Don't go too overboard in terms of audience participation though - see this as an opportunity to speak seriously about what & how you teach.
I'm around all weekend (have a cold & have to read a PhD) so feel free to ask any questions from this.
Good luck! 