This is an issue I am currently aware of. Some of the material displacement values didn't stick, for whatever reason, when I configured them. I really wanted every asset to be drag-and-drop (and for the most part, they are) but this remains a small issue. It is very easily remedied, however, by adjusting the displacement value after applying your material, something most users would typically do anyway.

No, I configured the material properties to work easily by allowing you to quickly adjust the X and Y scale using a single value. I couldn't think of a single time I would ever want to scale any material along a single axis, thus distorting a material. If you apply a material on a mesh and it's distorted, you need to UV unwrap it correctly. There are dozens of YouTube tutorials that will teach you how to UV unwrap your objects if you're a new user. Here's one I quickly found: https://www.youtube.com/watch?v=xFvW6kfClg0.

The websites I download the standard assets from often provide different resolutions. Some sites provide 1k to 4k materials and others only offer 2k to 16k. When they aren't available in the same, common resolution, I simply use a low-res asset for the SD collection, a high-res asset for HD, and a very high-res, yet still reasonably sized asset for the UHD collection.