Hey, I've got a Steven (different last name) testing for fifth kyu at my dojo soon too, and those are the same techniques! As you were specifically looking for these answers:
"looking for some advice on the kinds of mistakes they will look for and how strict the examiners are." I would say it depends on your teacher and your teachers proclivities. If you were at my dojo, I would say to relax and just try and do the techniques as they have been presented; try and remember the names of the techniques when they are called out (remember, the name of the attack preceeds the name of the technique, e.g., Shomen-uchi (downward strike) then ikkyo); don't try to do anything other than what you have practiced in class, remember, your teacher knows where you are already; to relax and have a good time. I can't say that I would be looking for mistakes, I would be looking for what you did right, and what could be improved upon for the next test (like entering the wrong way or something like this), and wouldn't be that strict on a first test. Sounds like you are USAF-ER, and this is the first test material. You should be serious, but also remember that it is your first test, and the big thing is just getting out there and doing it.
Best wishes on this!