Chip,
I can’t immediately help with Ann and William’s relationship. As I mentioned, Ann’s father’s name is blank on her marriage certificate, suggesting she didn’t know who he was, which often means she was illegitimate. (The groom’s father’s name is given so I don’t think it was a clerical mistake). But linking her to others when we don’t have her parents names will obviously be very difficult, unless you can show a strong DNA link perhaps.
In addition to the civil marriage certificate, there should also be a church record of the marriage (which sometimes contains additional information). Black Bog chapel was in Culmaine, part of Magheraculmany RC parish. (Black Bog chapel closed in 1957). The records are on-line on the nli site, but there are no marriages for February 1866. It appears the priest didn’t record them. Or perhaps there was a separate book which is lost.
You could search the parish records for Ann’s baptism to see if that shows who her parents were. https://registers.nli.ie
I looked in Griffiths Valuation for Portinode in 1862 and there were about 17 homes in the townland. There was just 1 Ward household and that was headed by Hugh Ward. I’d guess therefore that was where Ann lived and she is related to Hugh in some way.
http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
Hugh had plot 11a which was an 11 acre farm. His name is replaced in the Valuation Revision records (which take Griffiths forward) by John Ward in 1868, suggesting Hugh may have died.
https://www.nidirect.gov.uk/proni
I searched the statutory death records but did not find any matching death so can’t say for certain. Hugh may have died before 1864 which is when death registration began. (Griffiths clerks were sometimes out by a few years with their dates).
John was born c 1840. Here he is with his family in 1901:
http://www.census.nationalarchives.ie/pages/1901/Fermanagh/Drumrush/Portinode/1354080/
I noticed the marriage for what must be John’s sister on 24.4.1879. Mary Ward d/o Hugh married James Monaghan (widower & farmer) of Leaghan, at Ederney chapel. There were no Monaghan households in Leaghan in the 1901 census.