You will have to file a suit to prove that the entire amount for puchase of the Flat has been paid by you and that the name of the husband was added in the Sale Deed for convenience only. Also, the provisions of the Income Tax act provide for ownership of a property in proportion to the amount paid for acquiring the same.
If the terrace area is not a common terrace and has no entrance except from within the flat, then the society will not be entitled to put up any tower on the terrace area. You can file a suit against the society for restraining them from tresspassing into your property and also for removal of the tower.