Being Jewish is an ethnicity in of itself. Where Jews live is irrelevant to them being Jewish.
'Self Identify'....you mean White/Black/Hispanic/Asian?
sometimes other......yea if you give a handful of options 'white' will be selected by many people simply because it's the closest option not because you actually identify as white.
https://en.wikipedia.org/wiki/Jews
Most of the time when you pull someone over for a traffic violation you have no idea who's behind the wheel.
I also disagree that race cannot be a factor. If you know it's almost exclusively white drug dealers from a certain area coming into your city, it will most definitely be a factor in decision making. There's idealism and there are practical realities of law enforcement. It's a bit like deviating from game theory optimal approach while playing cards in order to exploit the mistakes of your weaker opponents. There's also nothing inherently wrong with making observations, having consensual encounters, etc.
I don't think your questions are as straight forward as you think they are because life is full of nuance and you're acting like everything is black and white. You are certainly entitled to ask any questions you like though don't expect easy answers that you think should exist. It's bit like going up to a lawyer and asking why the legal world doesn't function the way you think it should despite knowing almost nothing about it.