That is most likely because the preview mesh in there is going to be fairly small. So whatever math you are doing for units is probably very different at the two different scales.
I would avoid tweaking the settings for that view and instead place an actual mesh of your typical size in the world and tweak for that.
Then just give the location a good default location (ie, place another actor at your desired test spot and enter those location values). You should be able to scrub scalar parameters in the material and see them update in the world without having to compile the material.