If the timeout is caused by a long-running child process, you can easily fix that by upgrading python-gevent to 1.0+. It will prevent this kind of timeouts.

No problem :)

Yes, if you have set up any firewall, you should open the port yourself.

If your error is exactly "connection timed out", I'm 99% certain that this is a network problem. Try connecting to port 21 remotely using telnet

Check the logs in /var/log/exim

If you mean a virtualization hypervisor control plugin, no, it doesn't exist yet.

Please ensure that there's no firewall/NAT blocking the FTP port 21.