What sort of light settings are you using? Also, the light color matters too and you could use smaller values and the light will have less radiance. Like on the light you could use set_color(make_color_rgb(80, 80, 80));
When you dragged the image file into the clip window, did you drop it in the bottom right? After that drag the same image file into the material window in the albedo slot. That's the base color for your sprite or material and in the packer it is just there to preview things. You can tick the Lit box to see a sort of preview using Eclipse and then play with values. Once you have that figured out you can go to places like https://freepbr.com/ and just download materials that look like they would create what you need and just use the normal map. It will of course be a textured look and not exact to the sprites pixels. If you want that you can generate them as I think you already found the site, or there are other programs that generate much nicer normal maps.