In any residence district, there shall be a minimum required front yard as stated in the yard requirements for that particular district; provided, however, where lots comprising thirty percent or more of the frontage within 200 feet of either side lot line are developed with buildings at a greater or lesser setback, the required front yard shall be the average of these building setbacks and the minimum required front yard for the undeveloped lots. In computing the average setback, buildings located on reverse corner lots or entirely on the rear half of lots shall not be counted. The required front yard as computed herein need not exceed 50 feet in any case. Exceptions are listed in Section 196.03 of this Zoning Ordinance.