So is the screen anything more than a concept pointing to the fact that experience appears?
Well, yes. I'd say that we are using the word 'screen' is the conceptual pointer to the entire field of experience.
Can you experience a screen itself?
Or only appearances?
There are only the experiences, along with the entirety of them all together in the whole field (screen). The screen isn't experienced, it is experience itself.
What gives “here” its apparent location?
Are portal-like edges actually experienced continuously?
"Here" is the entire field, though there is no apparent 'elsewhere'--only the screen/field of experience and perception. Nothing else.
Observer and observed aren't separate when I look directly
If there is no separate observer now, what exactly is threatened by death?
I suppose nothing is actually threatened... there is the feeling and concept of fear of death.
Look at the immediate contraction that wants continuity.
Where is that contraction located? How does it manifest in the body right now?
What story immediately grows around it?
It's a sense of doership/ownership. Doesn't really have a specific location. It manifests in vague ways I can't put into words, but has a centralized face (my own) as a stand-in for agency.
The story is the story of the character who needs clarification.