I would try again but letter to CEO feels a little over the top. Makes it very DYKWIA. In cases like this where the policies are clear even if there is disagreement on how the message was passed along, I will push (and continue escalating) via the Cust Care route. Usually after a couple of escalation, they will make a goodwill gesture.

Additionally, 10 years to accumulate 70k+ points unfortunately does not translate to a HVC to Marriott.