I rebooted the office n66u and it seems to be okay now. From home, I'm able to access the office n66u webpage. Maybe the problem is gone. I did notice that it takes some time for the webpage to reflect a disconnected vpn client. I confirmed this by connecting and disconnecting from my mobile phone.
I have not confirmed the other problem still persists, where I disconnect the home n66u openvpn client from the office openvpn server. The home n66u openvpn client shows I'm disconnected, yet I can ping the office n66u from my home pc, which means the connection is still up.