[3:180] Allah would not leave the believers in the state in which you are, until He separated the wicked from the good. Nor would Allah reveal to you the unseen. But Allah chooses of His Messengers whom He pleases. Believe, therefore, in Allah and His Messengers. If you believe and be righteous, you shall have a great reward.
Sura Al Imran, Verse 180
Sura Al Imran is Madni Surah and was revealed after atleast 13 years of prophethood of AnHuzur :saw:. I think, by that time there was already a separation that was established between good and evil; between abu jahal and abu bakar
; between umar:razi: and abu lahab; etc etc.
But this ayat is suggesting that a time would come again when Allah will again separate good people from bad people. And Allah is saying that a messenger of Allah will do that, not any ordinary person.
So, if Quran says that there the door of prophethood is still open, we have to take meaning of ahadith which don’t go contradictory to Quran.
As far as question about ummat is concerned, we definitely belong to ummat of hadhrat muhammad :saw: because it was through the blessings of his ummat and total submission to his:saw: teachings that Hadhrat Mirza Ghulam Ahmad of Qadian:as: attained the status of prophet through Allah’s will.