Answer
(Fatwa: 114/95/L=1432)
(1 & 2) Your nikah was valid if you solemnized it in the presence of at least two witnesses. She cannot marry other man until you do not divorce her or she gets khula’. The consent of spouse (husband and wife) is necessary for khula’, khula cannot take place without your (husband’s) consent.
(3) You should not take any legal procedure rather you should try to solve it with mutual understanding. If there is no way left for conciliation, it is better to give her one talaq so that she could marry to someone else after passing iddah period and she had not to stay with her parents aimlessly.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband