I feel your pain!! I have a pattern for a diamond log cabin but it's paper pieced. In your case, my thoughts are, first starch the living daylights out of your fabric and second, try using slightly 'over-sized' strips (rather than your templates then trim to size after each round. BTW - I'm pretty sure the angle needs to be 60 degrees, not 45 degrees. Hang in there. It will be fabulous when you're finished.
Many quilters tend to be perfectionists. I let that go years ago. I encourage you to do the same. Be kind to yourself.
For whatever it's worth, I found this tutorial online. Maybe it might be of some help - - - -
https://cathymariequilts.com/2016/01...-cabin-blocks/