I bought and really like my Sumtoy mount for my FFIII on my SBEIII. My FastFireIII sight has the 3 MOA dot.
I have astigmatism as well and the "Auto" setting usually starbursts on me. However, the first and second manual setting don't do it as bad for me and I don't have a problem with it/don't notice it. It might be more noticeable/problematic on the 8 MOA dot.
I'm not sure where you are from, but if your area has a local facebook group for turkey hunters, someone on there might be willing to show you theirs.