I can COMPLETELY sympathize with your frustration after trying so hard and I think this group has made some great suggestions. Learning the 1/4" seam accurately takes a lot of patience and you need a way to check that you are doing it right. I use a 1/4" foot and a tape marker. Some people use those foot pads for your feet on the sewing machine to guide your fabric for 1/4" seam. I went through a similar torment after making several log cabin "squares", always something was off base. I still have to be careful and go slow and check check check.
I like your squares and your work.. the colors are great and the idea is sound. Don't give up! I won't if you won't!