Where a lawful structure exists at the effective date of adoption or amendment of the zoning ordinance which could not be built under the terms of the ordinance by reason of restrictions on area, lot coverage, height, yards, its location on the lot, or other requirements concerning the structure, such structure may be continued so long as it remains otherwise lawful, subject to the following provisions:
1. No such nonconforming structure may be enlarged or altered in such a way which increases its nonconformity, but any structure or portion thereof may be altered to decrease its nonconformity.
2. Should such nonconforming structure or nonconforming portion of structure be destroyed by any means or to any extent, it shall be allowed to be reconstructed to its previous dimensions or to dimensions which decrease the nonconformity, except in conformity with the provisions of this chapter.
3. Should such structure be moved for any reason for any distance whatever, it shall thereafter conform to the regulations for the district in which it is located after it is moved.