|You can't use 192.168.78.x on both sides of the routers or no routing can take place.|
These must be in bridged mode.
Your ip addressing is perfect if just using the routers as wireless switches. But this means they are connected to the firewall/switch via a lan port in each not wan port.
The usual setup in this situation is to do the following
connect the routers via their lan port not wan port
diable dhcp on both routers and have only the FW providing dhcp which will flow thru the wireless routers [now wireless switches]
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