i am a `screen` addict; but use it only in two patterns; naked `screen` with no command and then i am in a shell and do as i wish, or as `screen -L` to log the session for later archaeology.
in either of those use patterns, the C-a commands are available. if i `exit` or C-d, from the screen shell, i find myself at the outer shell prompt. sorry to have no useful advice on your use pattern, randy