HI Eddy, [Pls Rate if HELPS]
I am not sure whether your router can run as Proxy Server.
I would recommend, you can run some FreeWare Proxy Server Application.
Eg: WINPROXY
You can download and install on a WINDOWS PC and have the Public IP Assigned to one NIC and have another NIC connected to the LAN Switch.
So the Entire LAN Segment will have Proxy Server available. Also, with WIN Proxy you have several feature available to Manage / Control.
Hope I am Informative.
Pls Rate if helps
Best Regards,
Guru Prasad R