Because I am very, very stressed

Does anyone know roughly how long a 10 minute talk should be in terms of word count?

I know that I'm not supposed to write the entire script of the talk and read it out, but it'll be much easier to learn if I write it out first at least in bullet points. But I can't work out how long that should be.

I also don't understand why giving a talk should be so much scarier than teaching a class. How come I have a kind of intrinsic knowledge of how long it will take to present material in that context, but not in this context?

The 6-slide limit really doesn't help.