@Nuance - it seems like you might be mixing together a number of different concerns.
As far as your diagnosis no longer being PTSD - that would mean that the symptoms caused by your PTSD have decreased to a level where you may have occasional difficulty, but it's not a pervasive problem. That's nothing but good.
Whether the diagnosis is tied to your disability benefits/status...that's a different thing altogether, and you'd want to look into that.
Feeling like you are losing your identity by having recovered from diagnosable PTSD...that's a great thing to tackle in therapy. Many people who have had a long-term or chronic illness go through a period where they struggle to understand who they are, now that they are no longer "sick" in the same way they were before. In other words, this is a very understandable way to feel.
I think it would be better to address and work through the feelings that have come up for you (invalidation, fraud, etc), rather than try and argue that you should be diagnosed with PTSD, specifically, again.
Or, you could look at it this way - PTSD is (in many ways) made up of a laundry list of other diagnoses.
Depression
General Anxiety Disorder
Dissociative Disorder (not specified)
Sleep disturbance/Insomnia
Intermittent Explosive Disorder
.....and on and on, depending on how detailed one would want to get.
When one puts all those together in a specific way, plus a specific incident the symptoms can be traced to, it's diagnosed as PTSD.
When you stop having serious life-interference problems with one or more of the symptom groupings...then,
from a clinical perspective. it no longer meets the criteria for PTSD. But it doesn't mean you weren't diagnosed with it previously, and it doesn't mean those things never happened.