It sounds like you've done quite a bit of reading on this and are consulting with a mental health professional towards a diagnosis. While this might not be relevant to you, if you haven't already, you may want to also explore and discuss together the schizophrenia spectrum. It's also much broader than many people realize and has significant overlap with the dissociative spectrum. It doesn't have to involve the kinds of extreme hallucination or delusion stereotypically associated with schizophrenia itself.
For instance someone with Schizoid PD might experience a sense of switching between personas when they are exhibiting covert characteristics. Or a person with Schizotypal PD might experience shifts in identity as a result of sub-psychotic disturbances, or might turn their suspicion inward to ruminate on the nature of their own identity.
You likely have a stronger sense of established alters since you specifically mention OSDD-1b, but for folks experiencing symptoms of depersonalization/derealization, you might be interested in looking into and talking with a mental health professional about the negative symptoms of schizophrenia and the cluster A disorders to see if any of them resonate with you.
At any rate, bboy13, wishing you the best of luck exploring your mental health.