In all cases where a lot in single ownership, other than a through lot, is divided by a district boundary so that 50% or more of such lot lies in the less-restricted district, the regulations prescribed for the less-restricted district shall apply to the more-restricted district of said lot for a distance of not more than 30 feet from the zoning district boundary. For purposes of this chapter, the more-restricted district shall be deemed that district having regulations which prohibit the particular use intended to be made of said lot, or which sets higher standards with respect to setback, coverage, yards, screening, landscaping and similar requirements.