Conrad's said just about it all.   The songs were written for the music hall and for publication, but the relatively small area of distribution would place his repertoire somewhere in between pub songs, broadsides, and Tin Pan Alley. Wilson also travelled out to the pit villages to perform at soirees in miners' reading rooms and the like, where he was stated to have inspired the young Tommy Armstrong to start writing songs. As for the dialect, I'm sure Conrad's right to suspect that there'd be some stage-Geordie exaggeration, but it's very rare to hear anyone singing exactly as they speak anyway.

Another book you could look for which contains several Wilson songs is Allan's Tyneside Songs. This was reprinted in fascimile in the 1970s by (I think) Frank Graham.

As for the Alex Glasgow connection, the lovely wistful tune we now associate with "Sally Wheatley" is Alex Glasgow's.