You are so close Did you blocking connections from local lan (under local-basics tab)?
Then you need to open port53 tcp (local-ports tab) for dnsmasq requests from bnep0.
You can look in genwall local-lsof tab, there you should see dnsmasq listen on port 53 tcp.
Does the N900 has a bnep0 IP address (route-ip info tab)?
On that tab you could also click on dnsmasq and you will see hopefully two processes running.
I forgot to say all my tests were made with genwall 1.2.2 from extras-devel