If he bashed her head in with the bat (which we have learned did not happen, but hypothetically) , an excuse probably would not work.
OK then going along with your hypothetically speaking.
His actions either in shooting Reeva--after presumably assaulting her in some fashion, necessitating in his mind the shooting--were thought up in a panic or such and maybe he did not have too many options at that point?
He's done pretty good so far with his affidavit, no?