I have the map saved at almost the maximum allowed pixel count (It's at 3000x2200), so idk what the issue could be
That is the issue. The bigger you specify the map is, the more WarLight will have to zoom out to be able to fit it all, and zooming out makes army numbers smaller.
3000x2200 should only be needed if your map is massive enough to justify needing all that space. You should use smaller numbers.