For many patrons, a satisfactory response would be what has already been done, an apology, and a new one provided
A once in 2-years occurrence, and not even once in two years at the same store is just not an unreasonable complaint rate in my mind, but it's hard to call this a regular occurence.
I would have stopped with the complaint in the store, but I don't have an issue with sending an email as well. A third complaint seems over the top to me. Saying that you were emotionally not okay since you had a piece of bacon in your mouth which you promptly spit out is likely to make you seem overly dramatic and not lead to a productive conversation.
If you feel the need to send a third complaint, then you really should specify what you want to have happen or there is little chance they will be able to resolve this to your satisfaction.