That's more than necessary but shouldn't be the problem... here is the copy/paste I put up to most people, it is a little dated but still applies:
On the 5000 end, port forwarding needs to be done on a range of ports to the 5000, including:
67&68/UDP
69&20001/UDP
6800-6802/TCP
3998&3999/TCP
50098-50508/UDP
6004-6261/UDP
You also need to make sure the System NAT address (ie. the public IP address of the router forwarding ports to the 5000) is set properly in TWO places:
System\IP Settings\System NAT IP Address
System\Devices and Feature Codes\IP Connections\P6000\NAT IP Address
And to finish it all off, on the remote phones themselves in:
System\Devices and Feature Codes\Phones\<Ext num>\IP Settings
Change the NAT Address Type to NAT.