1. Banjocurl's right about the forelocks. Those are curled with curling irons, BTW, in order to make them shorter (since observant Jews don't cut them). It doesn't have to do with natural hair texture.
2. I'm Jewish with olive skin and dark, curly hair, but the two are not related. A portion of my dad's side of the family is Iberian/Turkish/Morrocan, and that seems to be what I've inherited. Accordingly, most people guess that I'm Latina/Catholic, or Arab or Persian/Muslim. My brother has extremely pale skin, straight sandy hair, blue eyes, and freckles. People never believe that we're related.
The problem with saying that people "look Jewish" is that it promotes stereotypes of ugliness/deformity, and of clannishness--that there are no ethnically Asian Jews, for example. Plus, there are a lot of different acenstrally Jewish ethnicities. It certainly doesn't mean that you're anti-Semitic, but it's like complimenting a Black woman for "being so articulate." At the same time, I'm not gonna contradict anyone for saying that Jerry Seinfeld looks Jewish.
3. It has never occurred to me to "pass." Being Jewish and being a quivering ball of angst are not genetically related, either