The answer to the question is affected by the answer to your bonus questions. I'll answer the second one first: There is no scenario in which Obama endorses either before one of them secures the nomination. If however he somehow did, that person (most likely Hillary based on what we know about who Obama preferred to succeed him) is the automatic winner. Both because Obama was extremely popular among Democrats and because it guarantees whoever he endorsed wins the African-American vote, to get into your first question. Without Obama's endorsement, however, it's a bit more difficult to say who would win the African-American vote. Biden would still be popular among black voters and his connection to Obama was closer, but Hillary was nonetheless still connected to Obama AND obviously Bill Clinton, who though no longer at his peak was still quite popular among the black community. My gut tells me Hillary probably wins the black vote, but it's a lot closer than it was compared to either her or Biden's real life wins over Bernie.
Speaking of Bernie, without him the progressive vs. moderate divide wouldn't be much of a thing (and in fact Hillary might be perceived as the more liberal candidate), but Biden would almost certainly take his place as the "anti-Hillary" candidate and thus do well with rural and WWC voters as well as men. I think Hillary does better with most urban voters, women, college-educated whites, and probably Hispanics. Considering the composition of the Democratic base, that coalition would probably have the upper hand, especially if she does win the black vote. It would however be close, closer than real 2016. Superdelegates would be needed to put Hillary over the top and avoid a contested contention, especially if she only narrowly wins the black vote and thus does not win those huge blowouts in the South.
I estimate that with this map Hillary would get around 2100 pledged delegates, Biden about 1900, with a fairly slim popular vote lead for Hillary. She would need superdelegates to get her over the 2382 mark needed to secure a majority. But as in real life, this shouldn't be much of a problem.
