In regards to Mc/Mac it is very subjective. My parents and grandparents before me used "Mc". When I was born the registar recorded my birth certificate as "Mac" so that is my legal name but I still use "Mc".
Mac in Gaelic means son. MacLean in Gaelic has several spellings, one being "MacGillean". This was shortened in English to McLean and later the "a" was put back in by many people. Cape Breton Island was heavily settled by Gaelic speaking folk from the Clearances and almost all of any clan used "Mc" when writing their name in English. Today most here use "Mac". A tour of any cemetery in Cape Breton containing headstones of these pioneers will quickly give proof to what I say.
                   Slainte,
                   Sandy