If all of your routers are on the same subnet (which they are; unless you're using an impossible subnet mask) then you don't need to forward anything from 1->2 and 2->3. The only one you have to forward any ports on is the main router that faces the internet (the one connected to the modem).
The other routers, as long as they're not plugged in to the WAN ports, are not functioning as routers but simply switches and so they will forward the requests transparently.
Again, NO configuration should be needed in the other routers (except turning off DHCP which you've probably already done).
As another Cisco trained guy, I would recommend strongly that you ditch the other routers and replace them with an 8 or 16 port switch with the router hanging off one port. You may actually see network speed improvements.
-r-
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