in an Asterisk CLI, is it possible when scrolling back to have the cursor not to jump back when new output hit the CLI and only revert after a key is pushed or after scrolling back to the bottom?
Alternatively, is it possible to limit the CLI output to a specific query (only events involving a specific extension)?
No, not possible.
But you can write your own tool and change behavour whatever you need.
For call-specific info you can check CEL or CDR.