Hey! I would add the cracks layer inside of the material in Unreal. There are plenty of material expressions and functions you can use to combine different textures in the material (like linear interpolate, multiply, blend angle corrected normal, ...). Got to get familiar with the material system and use the documentation.…
good find - I didn't know those dbuffer nodes existed. for the tiling issue - make a 2 or 3 versions of the material and use a world space mask (noise texture or something) to blend between them also go read about virtual textures - they're for making this sort of thing cheaper and better
HUGE UPDATE!: I somehow figured it all out through trial and error. I was able to use DBuffer nodes to apply a mask to decals applied to a given mesh (in my case the road mesh) to mask around the cracks. This was so tedious to figure out since I could not find any explanatory documentation online about masking decals.…