(Greek is my second native language)
- You understood Wikipedia correctly, a latin semicolon character is always interpreted as a questionmark.
- You will never find a semicolon used as anything else in (proper) Greek. There are no special cases. Though you'll commonly find people using a latin questionmark instead of a semicolon online.
- I don't think an ano telia would be appropriate for this. To be honest I don't even find a semicolon appropriate in English here.
I don't build with printing support but it sounds to me like it would be more appropriate to use a comma, or a dash.
J. Leclanche