Subject to the provisions of § 188-35 and except as otherwise provided in this chapter, the lawful use of land or buildings existing at the date of the adoption of this chapter may be continued, although such use or building does not conform to the regulations specified by this chapter for the zone in which such land or building is located: provided, however, that:

A nonconforming use shall be adjudged abandoned when there occurs an intention to abandon and some overt act or failure to act which carries a sufficient implication that the owner neither claims nor retains any interest in the subject matter of the abandonment.

No nonconforming use shall, if once changed into conforming use, be changed back to a nonconforming use.

A nonconforming structure or an existing structure on a nonconforming lot may be altered or repaired, but not enlarged or extended, unless the enlargement or extension does not violate any front, side or rear yard setback requirements or lot coverage requirements.

A nonconforming structure or building may be restored or repaired in the event of partial destruction thereof.

Whenever this chapter or the Zoning Map shall be modified, amended or supplemented, the foregoing provisions shall also apply to any nonconforming uses, structures or lots created thereby.