I don't understand, are you saying your fathers ISP blocks all inbound connections? I highly doubt any ISP is that excessive. (
Some do filter a few ports, i.e: port 80.).
How it can be taking "five to ten minutes" to connect is unknown, then again... we know nothing about the setup, you could even be exaggerating things.. (
Perhaps he's on dial up?).
Consider doing your father a favour, setup an OpenBSD router for him.. that way you can disable Windows firewall and use pf instead.