Hi Alex,
I didn't suggest you to use static routes, I have used static routes in my simulation to try to understand what the problem is and how can be solved.
On the routers you have, you can't setup an IP address to a vlan, like you do on the switch, unless the interfaces you mentioned (g0/0/0 -g0/0/3) are part of a switching module installed on the router.
If your g0/0/0 interfaces between the two routers are up and up, then the problem could be with bgp peer configuration.
If interfaces g0/0/0 are up on both routers but line protocol is down then your ping goes to the firewall first and you need to check if it allows pings on outside interface( i guess it is configured as an outside the one connecting to your secondary router).
You can use an extended ping from seondary and record the hops it goes thru, then you will know for sure which way it goes out of router.
One other suggestion is copy the running configurations from both routers, and if you have spare 2 routers connect them together like your topology, use loopback to simulate internet and firewalls and see if it works.
This is all I can suggest now based on the info you provided.
Good luck and hope that you will get to the bottom of it.
Eugen
