Hi Miriam -
Again, thank you for your response, your efforts and your guidance.
I've attached Michael's obituary and his death certificate, which lists his birth year as 1835 and his mother's name as Ellen Fenton. The only record I can find of his mother in the US is in the 1870 census - where she is listed by her married name (Ellen Bowler) and is living in Norwich with Michael and his family. You didn't find this because the family name was transcribed from the census as Boulee. Ellen is listed as being 55, which puts her birth in Ireland around 1815. Regarding the 1900 census, for whatever reason Michael is not listed with his family at their home in Norwich (several of his adult children - including my grandfather James - were living at home with their mother). Michael is listed at that address in the 1900 Norwich City Directory so I have no clue why he isn't listed in the census.
I have no info regarding whether Ellen Fenton Bowler was a widow other than Michael's obit saying he came to the US in 1845 with his mother, no mention of a father or siblings. However, I couldn't find any John Bowler in the US/Norwich which would indicate being Michael's father. Regarding Catherine being Michael's sister, Michael's oldest girl is named Mary (probably after her mother - Michael's wife Mary); his 2nd girl is named Ellen, which was both Michael's mother and mother-in-law's name; his 3rd girl is named Catherine - possibly after a sister?
I have nothing that indicates Michael was a soldier in the American Civil War. If he was his mother's only child, he would have been able to avoid the draft as her sole source of support.
Again, thank you for all of your help. I have a number of questions regarding other ancestors - 7 of my 8 great-grandparents emigrated from Ireland - so I may be imposing on your helpfulness again soon!
Best regards, Peter