I follow your experiments, because I have done a number of them myself for a little time ago.
I did not find any good enough skype gateways (8-9 months ago), but I also experimented with diferent ways of comming trough the blocked internet connections.
One option that I tested out and actually got working was Asterisk and IP telephony trough a OpenVPN encrypted tunnel. It worked but sound quality was not good enough. (If I do not remeber it wrong, I think I had iptelephony trough a TCP 80 and a TCP 443 tunnel.)
What ended up at the two solutions that worked good enough and that I am still using is these:
SIP is a difficult protocol that is easy to block. IAX2, the native Asterisk protocol is a protocol that is possible to get trough, some way, allmost everywhere. I don't remeber what is FreePBX, is it Asterisk based ? (I think so, I'm only running a Asterisk rpm on my SME server.)
Anyhow what I'm doing is to use Asterisk via IAX2 on UDP port 53. This is the standard port/protocol for dns inquires during ordinary web browsing, so this solution works allmost everywhere. (But it depends a bit how your ISP has blocked for your ip telephony, and what you will try to obtain.)
An quite good IAX2 client that can connect to IAX2 standard port or UDP 53 is Zoiper.
http://www.zoiper.com/On most hotspot with some restrictions Zoiper/UDP53/Aterisk works bether and quicker and more easy than the Skype client.
For the mobile telephone part of my project I first bought a SIP/GSM gateway. It worked but it had rather poor technical quality, so I just experimented with some alternatives. The solution I use now, is to program all my international contacts as extensions on my Asterisk server. When I call an incomming number, I can just push the extension number, and I will be transfered via a preprogammed route to different places in the world. This makes it possible to make international calls to approx same price as a local call. (And with the SIP/GSM gateway it could be allmost for free, but with some technical bugs, from time to time.)
There is also one other option that I used/tested for a while. This is the free PBXES Asterisk server. I think it is possible to make it work together with your own local server. (And PBXES is not prevented by a firewall)
https://www2.pbxes.com/index_e.phpI used both the SIP/GSM gateway and PBXES for a while, but in the end it ended up with the simple solutions I am using now. (Zero bugs or problems during more than 6 months.)
For me the Skype/Sip gatway alternative was also a solution that I did not use, but I find it quite interesting, if it should come up a solution, where thil will work "in a good enough way".
Please post your "findings" I would like to do some tests as well.
Another option - Gizmo is an alternative to skype, and I believe Gismo has a some kind of "buildt in SIP gateway":
http://gizmo5.com/pc/asterisk/ It's a rather long time since I tested/used Gizmo so I'm not updated on that.
One other option I just found (never tested):
http://www.chanskype.com/