This type of setup isn't common, so we haven't tested it very extensively, but I can tell you if you aren't getting an IP address in the app, it's usually due to an inability to hit the API. You are seeing 0.0.0.0 as the IP in the app, correct?
You should be able to edit the dnsmasq config via Tomato's GUI at "Advanced -> DHCP/DNS -> Dnsmasq custom configuration" and add the following lines:
Let us know if that helps.
Also, have you already tried all protocol options available?