1) Your server is using custom weapons.ini settings. You need to use the original unmodified weapons.ini if you don't want your server to appear as modded.
2) Don't know. You sure your server allows this many players? Check your Max Players setting.
3) It just happens sometimes. Don't know why is that and what it does, but I saw it happen on other servers many times.
I do have a similar question though.
I once tried hosting a server and loaded a custom weapons.ini. After that my server had (WM) in its name (which is expected, of course). But when I loaded default weapons.ini - my server would still appear with (WM) even several hours after switching to default weapons.ini. How can I revert the server back to non-modded without having to restart it?