As long as his mother was American he automatically is a citizen...
As well as his actual father. Frank Marshall Davis.
Yes, but not a natural born citizen. Was he born overseas? It seems to me as I recall there was some indication he received Fulbright scholarships, which are designated for Americans to study abroad - but, also as well, the converse - foreigners to study in America. Everybody seemed to claim he was Kenyan, until later on, when it became problematic due to it being prohibited. What about his Connecticut social security number? Too many gaps in the record, everything is locked up tight as a drum, his selective service records, his grades. For all we know he failed lunch.
And as long as his father is a British subject, HE is a British subject.
Citizen is not the same as natural born citizen as enunciated in the Constitution.