I find it strange that the iPhone is able to connect and communicate through the firewall.
Don't you have another i386 desktop install a WiFi card and OpenBSD on it and try that as wireless client ?
To eliminate the rum0 hardware, you could go to a Mom and Pop shop in the neighbourhood and get a hardware AP like I have, on a NoCureNoPay basis
For less then 100 bucks, why continue struggling?
You first plug it on your home ethernet. If that works then can add another NIC to your router. connect the hardware AP into the new NIC, so can give the wifi a subnet of its own, separate from the wired Lan.