First, the current firmware in my router sucks, so it's harder than hell to get to accept my password to make changes. I was lucky to get it to forward port 80. Otherwise, I WOULD use port-triggering to forward a different port request to port 80. Port 80 works within the LAN, so once the connection gets that far, I don't have to worry about it. I have have to keep my router forwarding port 80 to my computer, since I don't think there's a way to get Xitami to listen to another port. I tried DMZ, but that didn't work (more evidence it's the ISP). I'm not worried about using DMZ because I also use Zonealarm Pro. That's not the problem either because it doesn't work whether or not Zonealarm is on.
No, my ISP doesn't block all inbound connections. I know this because I can upload files in my file sharing programs.

Im going to try to reinstall the firmware upgrade in my router. Maybe it will be more agreeable to configuration changes after that.