aaiyar

Sorry, I won't read lengthy posts that contain already the most problematic part in the title (Lamobo R1). If you want to rely on this crappy piece of hardware and if the R1 should act as a bridge between LAN and WLAN then I would recommend configuring the whole thing just like that. And that means configuring a bridge when the device should be used as bridge!
 
I don't get it why everyone always wants to deal with TCP/IP packets on layer 3 to solve problems that do not exist when you do it correctly at layer 2 (bridging not routing and not dealing with TCP/IP packets but 802.11 frames instead)
 
BTW: Unless you do not want to get a bit familiar with networking this won't be solvable. You refer to 'passthrough' which could be either routing (TCP/IP, layer 3) or bridging (layer 2). I would recommend googling for 'debian bridge ebtables' to set up the stuff at layer 2 instead of enabling routing capabilities on the R1 (since then you would have to learn concepts like netmasks and so on)