I think I figured it out.
I typed a piece of text and right-clicked on it and selected "Hyperlink". In the General tab, under "Link To; Data Source:", I used the "concat" function to stitch the fields together:
concat(d:t_Subfolders/d:t_Discplines/@Network_path,d:t_Subfolders/@Subfolder, @FileName)
The fields in bold correspond to the fields in my first post (fields are case-sensitive, so be very careful when typing in the expression). I used this same expression for the "Display" information. The text now changed into some sort of "control", kinda like a text box, so then I cut and pasted it in my repeating table. When I run the query, now I get clickable hyperlinks that open the files.