If the problem is in fact your traffic is successfully leaving through the VPN but not coming back, that sounds a lot like a reverse path filter (link to post) problem I ran into. Reverse path filter is the name of the function in linux, I am not sure what bsd calls its analog. But with reverse path filter turned on, when my traffic returned over the vpn tunnel interface, the traffic would be silently dropped since the filter expected traffic from a non-local address to come in over the wan interface. Once I disabled reverse path filtering, return traffic over the vpn interface made it all the way back to the local hosts.