Don't most people with PTSD have anxiety related symptoms throughout the day?
The sets of criteria for diagnosing PTSD are rather far-ranging. It's not a requirement of the disorder to have anxiety-related symptoms throughout the day.
According to the DSM-5 (which is the diagnostic manual for all psychiatric disorders), Acute Stress Disorder can be diagnosed up to one month following a traumatic incident; after that, if the trauma meets the criteria listed for PTSD, and if the individual exhibits enough of the other criteria (symptom sets) for PTSD, a diagnosis can be given. If the symptoms are better explained by another disorder, than one is given that other diagnosis.
What you are describing, to us non-doctors, sounds more like some kind of anxiety or panic disorder.
The good news is, you are putting yourself through a kind of exposure therapy, and it sounds like it's working. The kinds of setbacks you mention in your OP - that unexpected rush of adrenaline you had - is not uncommon. It's to be worked through, just as you have been working through it.
You can't be diagnosed with GAD until you've had consistent symptoms for 6 months - and even then, you don't sound to me like you meet the criteria; the anxiety does indeed have to be generalized (come from multiple sources). Panic Disorder has to occur unexpectedly, and your panic attacks seem to be on a timetable.
My personal armchair-diagnosis (backed up with zero medical degree)? - You're developing a phobia. Phobia is an actual disorder, and it's nothing to sneeze at. It's in one of five categories, and symptoms all group around the phobia. What you've attached to is the time of day that you experienced a severe fright - so your developing phobia is manifesting primarily at that time.
Phobias also cannot be diagnosed for 6 months. Why? Because it's really not unnatural to have the kind of extended trouble that you are having, after a terrifying experience. But if it persists longer than 6 months, it's 'settled' into a disorder.
The DSM is really just a big-ass book of codes; a way to organize symptoms. And without going to see someone who is trained in using it (psychiatrist or psychologist, some therapists are qualified to diagnose but not all), you won't really know.
My personal recommendation is to keep doing what you are doing - don't be daunted by the setback, it's just your mind holding onto some of the fear. If you are up for it, try and get into doing some other activities that support anxiety management - you're doing diet and exercise, which is great - you could look into guided meditation, you could see if you can take a mindfulness class...all this stuff helps.
And if it's still no better at the six month-mark, go in and see someone for another diagnosis. But, if you have been making headway doing the exposure therapy, then by all means - keep doing it! It's working, which means it's addressing the problem.