Like, I don't know, sounds as if life has got better and so you think you should also feel better??? It's interesting that you're wondering if your body and all its systems are stuck in high anxiety.
When I was 25 I had a kid with a life threatening and life limiting condition. He's still around now but requires a lot of care. I do believe that living through enormous amounts of unrelenting stress did for me. The only way I cope is with weekly f2f therapy because my head's blown - 6+ years and counting. Basically, it allows me to ring-fence my emotional labour and now I'm not pure exhausted all the time.
I also have a herbalist and a massage therapist. While I'm aware this makes me sound like a princess, I reckon the cumulative total of 1,000s of hours in ICU over the years, watching other kids / people die, means that without support I wouldn't actually be here.
Severe anxiety and depression looks an awful lot like terrible fatigue. Presumably, you've completed the GAD7 and PHQ9 questionnaires.
On a completely different note, you mention a restrictive diet, histamine issues and your immune system. Are you seeing an immunologist?
Finally, obviously, it's possible for various conditions to be operating at the same time. For me, the therapist and herbalist helped me to disentangle what was going on.