How do I resize the iOS simulator?
You can't. I've been an iOS software developer for two years and I haven't been able to find a way do this. I have tried to find solutions to this but came up with nothing. I'd love to be proven wrong, but I'm 99% certain there's no way to do this.

When my screen is too small I use 50% scale window, which is ought to be enough until I hook up my big monitor again at home.

EDIT: As of Xcode 9, you can resize it to any way you want from the corner of the simulator.