The outbound leg should be to channel local/0777$did@from-internal, then it will use your outbound routes
Looks okay, assuming the AGI file works
Never (ever!) use from-pstn-custom. Use your own context that ends with a goto to from-pstn, and direct trunk calls to this new context. Every line you put in from-pstn-custom overwrites a line of generated FreePBX dialplan, and there is an early line that is critical for system security. Do not be lulled into this habit because it’s working in your tests.