Really can't explain why that screen is empty for you. When I checked mine my SP3 Service Status had no data. So I made a call using SP3 (which I rarely do) and the stats immediately showed up (OBi 200). I was going to ask if you had any Underruns but I guess that's out.
When looking at the Call Status screen I assume you see the RTP packet and byte count increment when you refresh?
Have you changed your Channel Rx Gain setting yet to see if it made any difference to the called party?
Have you tried using a softphone (on either a cell phone or computer) to see if it works without issue going thru the Comcast router? You can download Phonerlite (free) for your computer and try that. I personally use Phonerlite and also use
VoIP.ms (along with 3 OBi devices) without issue thru a Comcast gateway modem. In addition, I also use a Netgear router which means I'm double NATted (which is NOT recommended) yet I have zero issues using 3 OBi devices with 8 different service providers and I have much less bandwidth than you do (25/5). I do this because some of my devices seem to work better using the Comcast AP.
Since all your hardware is already configured for the Comcast gateway modem it may be easier/quicker to just put your OBi in the DMZ to see if it makes any difference before adding your ASUS back into the mix. Just a thought.