All those records are the same, v547p 606 is the Somerville record, v547 p342 is the Cambridge.
The Cambridge record is hand written and the Somerville is typed. I really zoomed in on the handwritten last name for Eunice and I don’t think it is McGonagle ( which is how it is typed in Somerville), knowing now that her middle name was Winifred I can see that it looks more like Eunice WGonagle. Later when I have time to fool around with it, I will try to get a copy you can read, so you can see what it looks like yourself. I think I’ll have to print it and rescan it to get the picture. But it starts to look like Eunice’s name was just misheard/written, (maybe the Irish accent and the Boston ears ?) and Ellen’s name is just wrong. I have one ancester who’s father Michael is listed as Daniel on her marriage, there aren’t any Daniel’s in that family, but I know it’s her.
In the Cambridge record there is a bracket around 3 records, indicating that the clergyman performed three ceremonies that day, maybe he just got names confused. I’m not sure who informs these civil records. I had thought that Cambridge, where they got married, passed the information to Somerville, but the written record doesn’t say “Co. Tipperary” ( is that correct for your Catherine? ) and the Somerville record does. Both records use the same date name and address information.
On the Eunice death record, where it says “ Daniel Campbell & Catherine. Are the first names right ?
Maybe her mother is the Campbell. It’s a very faded recorded, ( I won't be able to copy that) and looking at other entries, I don’t think a meticulous person was keeping that ledger. Eunice’s age says “unknown” , other peoples records have partial entries and blank boxes.
I only see the death records for Charles Daniel’s parents in Easton I haven’t seen any marriage record - were they married in Massachusetts?