Exceptions. Any structure devoted to a non-conforming dwelling use (e.g., a dwelling located in a non-dwelling district where such uses are not permitted) may be remodeled, extended, expanded and enlarged; provided that, after any such remodeling, extension, expansion, or enlargement, such structure shall not be used to accommodate a greater number of dwelling units than such structure accommodated prior to any such work, and provided that such work does not create any dimensional non-conformities, except as may be authorized under Section 400.305 below. This Subsection shall not be deemed to authorize any violation of Section 400.300(A)(5) and (6) or Section 400.300(B), (C), (D), or (E).