That quite interesting (esp the story about Champ Clark helping avert a lynching). I don't know about Champ Clark's racial politics more broadly, however.
Me neither; but the fact that he attended the opening of that training school (in his position I'm sure he could have found some excuse not to, had he wished) suggests that he was ok with the idea of Blacks becoming Army officers; so he might well have been ok with having them in other federal positions also.
it seems likely that any Democrat at the time would have enabled policies like Wilson's.
Did Grover Cleveland purge Blacks from government posits? I hadn't heard of that. And given that Clark, since leaving KY as a young man, had been arguably more Midwestern than Southern, his Cabinet might have been less Southern in composition than Wilson's.
To be clear, a GOP administration would have been better for African-Americans than Wilson's.
OTOH Wilson's Republican successors did not reverse his action, which suggest that GOP interest in Black rights was at a very low ebb.