If attempting a remote extension without using the tunnel (sip proxy or tunnel for softphone) 9000-9049 UDP need to be forwarded correctly and 5060 as mention before, be sure STUN is setup properly and rport and keep alives setup (15-20 sec.)
Static port mappings are necessary also. maybe I missed some comments and I hope not, it wouldn't matter MAC or PC, maybe I am missing something but really 5060 forwarded correctly and 9000-9049 forwarded should work. It depends on the router and proper configuration. And STUN correctly setup as well as rport enabled and keep alives. Direct remote extensions can be a pain and there is more router config and port mapping then anything stopping you from your goal. good luck!!