I had contacted the Archdiocese and got some information on the family.(it took about a year to get a response - I recommend contacting them ASAP if you're thinking of getting information there...).
Here's my updated information:
John Newton Henderson married Susanna McDevitt 15 May 1893 at St. Charles Borromeo Church in Philadelphia.Witnesses were James McDevitt and Frances McCue (or Malone?).Rev. T. Quinn.I got both the church and the county record.
John Newton Henderson was born 25 Dec 1862 in Philadelphia.I think he was born "John N. Mix" from the 1880 census.
Susanna McDevitt was born 10 Oct 1868 in Gloucester, Camden Co, NJ.She was baptized at St. Mary's Catholic Church in Camden.Witnesses were Edward McDevitt and Mary Lyons?
Susanna's parents were John McDevitt and Susanna Dougherty (a later record said Susanna Doyle).They came first to NJ and then PA.Since their first daughter was born in Ireland, Catharine E (Kate) 5 Apr 1865, I think this is the John McDevitt and Susanna on the ship Washington, 17 Jul 1865.They also had a son James William McDevitt, born 22 Jul 1873, baptized 3 Aug 1873 at St. Charles Borromeo, though later he went by "James J".
James was likely the witness at the John Henderson marriage.I don't know who the Edward McDevitt was in 1868.I'm guessing a relative.There's a couple Edward's across the river in Philadelphia at the time.
Susan McDevitt, wife of John, died 31 Jan 1900 in Philadelphia.I don't know when John McDevitt died, but it seems it was after 1900.
Susan McDevitt, wife of John Henderson, died 12 Nov 1898 of TB.Their children were placed in an orphanage shortly after.