Hi
I do follow your line of reasoning, and it may be right. I think it's probably me being a pain! Joseph Walton as a marriage witness doesn't bother me over much, it's the subsequent naming of the first son as Joseph that makes me wonder.
Are there two baptism records for John's son Joseph?
I've mentioned the one at St Andrew on 27 Nov 1818. There is a slightly earlier one on FreeReg,
11 Nov 1818, St John
Joseph, son of John and Jane Walton
Father a Shoe maker
Abode Barracks
It notes "Baptism at the Lying-in Hospital"
EDIT
Have now found the image in the BTs
https://www.familysearch.org/ark:/61903/3:1:S3HT-XXZ7-6V1?i=626&cc=1309819&cat=1809373Barracks as abode throws me a bit. But looking for Joseph Waltons in Newcastle and not finding a lot in 1841, there is a burial at St Andrew, 4 Feb 1829, Joseph Walton, age 58. Abode given is just "this Parish"
BT here
https://www.familysearch.org/ark:/61903/3:1:S3HT-67F3-J9K?i=226&cc=1309819&cat=1809360A death announcement in the Newcastle Courant, 7 Feb 1829
On the 1st inst. at the Barracks, near this town, Mr Joseph Walton, aged 58, twenty of which he was Barrack Serjeant.
No indication as to whether he was married or not, sorry to go off on a tangent again. I would bear it mind (no more than that!)
John
FURTHER EDIT!
I don't do ancestry trees for info, but Joseph died 1829 seems to be in some. Might be able to eliminate him perhaps.