Language and culture, are constituents of the definition of ethnicity. I think you are confusing ethnicity with race. You are stressing too much on the blood and race, but you are forgetting that those Urdu speaking Pathans in India and else where, have intermingled so much with locals , that they may not even have 0.1% of "Pashtun blood" in their veins.......then again what exactly is Pashtun blood?. Our ancestors were Sakas, Hepthalies, Kushans and number of east Iranian groups.
We Pashtuns have a very strict definition of Pashtun. You cease to be a Pashtun, when you and your family's mother tongue is no longer Pashto. Beside speaking it, we also have a term "doing Pashto", "living with Pashto", is also a criteria. Our Pashto is not merely a language, its packaged with heritage and particular Pashtun behavior.
You dont need to do "months" of research on us from web, that will be waste of time. You need to give three "fvks" to know about Pashtuns