You internet researchers on here really make me laugh. If you got your facts from wikipedia or google then its probably full of shit. These sites use the undocumented facts given to them by people. This is why there is an update button included, so other people can correct information. I am a historian who holds two doctorates. I do research for major historical societies for a living. The John Hanson the OP referred to was a white congressman from Maryland. The black John Hanson didn't come into prominence until the 1850's when there was a growing popularity in the idea of sending African Americans back to Africa. That should end the confusion.
As for the treatment of "free" blacks during that time, your facts are wrong. There were several free black men who held office in local municipalities and were up standing citizens of their region. Most of these people lived in what was called the New England states (NY, Mass, Del, RI, Conn). Although there was also the chance that unscrupulous whites would steal free blacks away into slavery, every free black man was not considered "non-slave". Crispus Attucks, for example, was a free black and was well respected in his region. The night he was shot, he was in the local pub with other colonists drinking and socializing.
If you really want to know who was the first President of African descent, it would be Warren G. Harding. I posted this on this board a few years back. Warren's maternal grandmother was a mulatto women, the product of a white slave owner and and a slave girl. As a child, Warren recognized her as his grandmother and even had pictures of him sitting on her lap. When he first entered into politics, he still acknowledged her. Shortly after winning the white house, two reporters who had discovered his lineage asked about it in a press conference. Warren became outraged, vehemently denied it and banned these two reporters from further press conferences. In addition, the pictures of him and his grandmother vanished only to resurface about 15 years ago. Harding knew that disclosing his lineage would mean his political downfall. He never mentioned her again. The two reporters published a book about Harding lineage several years later. I've read the book. I'll see if I can find a copy and post some excerpts from it on here later.