The fact that the bullet first hit Mrs Oulson indicates that at the time of the shooting Mrs Oulson was standing in the gap between Oulson and Reeves thus making the "feared for his life" claim pathetically hollow -- unless he is claiming that he was afraid that Mrs Oulson was going to attack him.
The truth is that he shot him in retribution for tossing popcorn at him as he was heard to say:
"that'll teach you to throw popcorn in my face".
That's not fear for your life. That's shooting someone for what they did rather than what you fear that they might do -- and that makes it criminal.
Again this has nothing to do with what you think only with what he thought in that split second.
It has all the appearance that his wife was trying to hold him back from attacking the elderly retired gentleman by restraining him physically. She put her hand on her husbands chest to hold him back. She didn't grab him and try and pull him out of the way.