Return and size down if possible. Heel pads should be a last resort if you get stuck with a pair that is too big, ect.
The width of the whole last, because it goes from E/C to D/B.
Also, those are nice!
Edit: If funds allow, keep that pair for now and order 7E. If it's too narrow, you might have to just do tongue pad unless you can find a EE.
Have you tried them on with socks? The fit might be perfect with medium thickness socks.