(1) If the boy and girl themselves or their wakil do ijab-o-qubul in the presence of two Muslim witnesses then nikah shall be valid. However it is sunnah to read the khutbah before nikah and it is also mustahab to do nikah in the mosque. The boy or his wakil may also read the khutbah and perform nikah even without a Qazi or Molvi.
(2) It is necessary that there are two women with one man. Only by one man and one woman the quorum of witness shall not be complete because the quorum of nikah as per the Holy Quran is two males or one male and two women.
(3) Nikah-Nama with signature or thumb impression is a documentary note which is written so that it may be of help at the time of need. Nikah becomes valid if done verbally in the presence of two witnesses.
Allah knows Best!
Darul Uloom Deoband