I see you are using an old version, I recommended to update to latest version.
1. There is a settings in Dashboard > Front End PM PRO > Settings > Recipient for “Can send to users” which was unchecked. So that other users could not send message to multiple recipients. I have checked it now. Please see that other users can send to multiple users now.
2. In latest version admin can send reply to any message. You can update to get this feature.
3. One characters cut in From Name in email, that is solved in next version which will be released this week.