Welcome to OCDO.
I hear trigger control issues that are solved by lots of practice. Try an attached laser (not a target laser, maybe just a pen taped to the barrel) and pulling the trigger on a snap-cap until the dot on the wall is stable.
When the trigger pull is smooth and gentle then adjust your sight picture. I was taught full-pumpkin, with the ten ring sitting on the front post. I have taught half-pumpkin, with the X sitting on the front post.
Flinch issues can be diagnosed with snap-caps mixed into a magazine of live rounds. You'll see the flinch on a snap-cap! I don't know how to cure flinch. I have never used hearing protection for their effect on potential flinch.