Ya, wireless ISP huh? Hmm, not the greatest for gaming I must say. Preferred is wired Cable or DSL.
From the looks of yoru IP address on the WAN, your getting a Private IP address from the ISP Modem/Antenna. Not sure if your ISP allows bridging or that modem supports it.
Does the modem have a management pages? If it does, I would try to see if it has a DMZ option, and input the 4500s' IP address of .1.3 into the DMZ on the modem, if it has this option.
Right now your probably dealing with double NAT situation.