I'm glad you got it working (partially) !
WRT to one-way audio, do you have 'NAT Mapping Enable' and 'NAT Keep Alive Enable' set to 'Yes'? (Found on the Line 1 tab).
If you have an ADSL modem in router (NAT) mode, you could also have a look to see whether the SIP ALG is enabled on your ADSL modem. It seems that a lot of modems have a crappy implementation that screws up SIP instead of fixing it.