Yes, it probably would have, but I think Wilder could have won in 1992.
I think not. He would have been humiliated by President Bush in the general had he won the nomination. As both Tweed and Straha have stated earlier, no African-American politician, with roots in the Civil Rights movement and a descendant of slaves, which Governor Wilder was would have no chance.
As for the question, 1996 is most likely the answer however it would depend on numerous factors which would cause General Powell to defeat President Clinton in the general, such as the infamous Perot.