Your right about Dowdall but the Marriage Registry shows she was a widow called Mary Buckley at the time she married John Grace, her father was John Dowdall.
Elizabeth's birth record shows her name as Buckley too. It looks like she married John Buckley in 1880.
She had twin daughters by her first husband in 1881 called Mary & Elizabeth Buckley, his occupation was "Law Clerk".
Mary Grace is the 1901 and 1911 census. Her father was James so she is probably the Mary Dowdall born at Harold's Cross in 1860 - click here for link. More could be done with her but I'm not sure that investigating the District Nurse will reveal more about your family.
Not sure I can do much with Mary Jane Lytle. The name Lytle is practically unknown in Dublin, it appears to be an Ulster name. Sometimes it is transcribed as Lytte, as this Mary Jane Lytle census record was. On the other hand Little is too common to research easily.
Do you have a family tree you could load on to Wikitree? That might help identify more leads.