Yields on EDI-EWR are astonishingly good, although I suspect GLA-EWR is more variable. You'll struggle to get a EDI-EWRvv for under £450 in summer or £300 in winter. November is a shoulder month on both routes, which suggests your theory on the weekend break may well be correct. While EDI is a strong C destination, I imagine the C yields are a bit more variable. Apparently the 9am EDI-EWR flight gets more O&D than the 12pm one, which I find a bit surprising, but there you go.

As for DL, I suspect they will be lucky to get 60% loads (CO gets 93% average out of EDI) and little of any C revenue will be full fare.