Hello there I am thinking there is a connection to your McCullough's you are looking for and my McCullough family. I am a descendant of John McCullough's brother Thomas McCullough.
1. Regarding John McCullough Sr.'s marriage to (Johanna Hannan) it lists his father's name as F. McCullough & N. Glasgow.
2. I have a Jon McCullough Sr (same wife and family and dates and everything) but his father is actually called Thomas McCullough mother Nancy Glasgow. It looks like this "Ontario, Canada, County Marriage Registers, 1858-1869 on ancestry.com" record has a few mispellings and errors in names and you can only see the transcript... not the original document. When you look at the same record in familysearch.org you can see both the indexed version and the original document. The familysearch.org document is correct it shows very clearly that John McCullough Sr.'s father was T. Mccullough not "F" even his spouse and her family name is Hannan and spelled clearly.
here's the link:
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS7D-BSBP-H?i=145&cc=2568642&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AQ2CB-H1KKlet me know if that link works.
3. I have this John McCullough in my family tree, in fact I have a whole McCullough family history book! I'd be happy to share with you all written by Mary Van Gorden. Its also on familysearch.org, its called "The Life and Ancestry of Ellen Mary "Nellie" (McCullough) Van Gorden."
Here's the link:
http://www.familysearch.org/library/books/idurl/1/857391 4. For reference, if you go to page 66 in the book (pg 79 of digital document) it tells you details about the life of Thomas McCullough Sr. and Nancy Glasgow (John McCullough's Sr. parents). This is all we know about them. You do need to be a member of Familysearch.org in order to access the book. Its all free so I hope this helps.
OK so now I am extremely interested in the documents you have and have mentioned in this thread. You see we don't show record of a brother named William McCullough and we only know that they came from Ireland (see 68-69 for life sketch of Thomas & Nancy McCullough.) Is there a way for me to get the information you have and piece it together some more? I am extremely interested in this discussion and don't have any of the records you mentioned except the census records you mentioned.
I am hoping that by combining the records I will have a better documented family tree.
Let me know if you can send me those documents (or where I can find them)
I'm very interested in the information you have on them going to and from Canada from Ireland. I have since found record thanks to "keady123" who gave me the town & County the family owned land... I have found record of a Thomas McCullough leasing land in the Derrynoose Parish, County Armagh, in the Derryhennet Townland, Ireland. I've attached the records of this.