Hey Kojote,
Welcome to Psychcentral forums!
I do *exactly* what you do - imagine characters - be lost in their world, they experience violence, extreme emotions and I could not stop thinking about them. Situation was that, I cared about "their" life more than about my own.
When you experience abuse or just if you grew up feeling unloved by your parents, mind dissociates to avoid feeling the pain. Ignoring reality is a large part of survival, because you want to be a functioning member of the society - or atleast come across as one.
I don't experience "floating" or derealization, but a lot of people do.
One thing that did help me to some extent was to write about my experiences.
And I really recommend the book - Body Keeps Score by Bessel van der Kolk - this author has covered derealization, floating, not able to feel your body, no sense of time....it took me close to 4 readings to truly appreciate the book and you'd find some of your answers here.
I wish you best and all my love.