An 'in full' reply.
Sandra - thank you so much for all of this. It's an enormous amount of research!
I'm a little concerned about Margaret's stated birth date of March 1882. She was baptised in 1876. This seems a huge difference. Then again, my Grandad - her cousin - travelled on a false birth certificate that made him 7 years younger in order to get him more work. Maybe Margaret was doing similar? This way she was married at 30 rather than at 36. Did that make her more desireable to Mr. Joyce?
So Margaret left the US for Ireland in 1914 and was still stuck there in 1920, having no US passport? You've typed "Left Ireland 1882-1904 and 1914-1920) which is a little confusing. Is this implying she went to the US as a baby? If so, then this really can't be her.
She did have a brother back in Ireland, and her and Tom are supposed to have visited.
Hard to state family likeness based on the photo, but none is jumping to mind.
One story states that Margaret returned to Ireland as a widow with both her children. This wouldn't be possible if we accept her death date as 1959, but Tom's as 1964.
Is the final passenger list referring to Tom Joyce b. 27/10/1879 travelling from Ireland to Philadelphia in 1926?
Again, huge thanks for all this...but it does raise some doubts!