It sounds like a routing issue; either the router is not routing between Ethernet and WAN interfaces when in wireless bridge mode or the DHCP server isn't providing a gateway so you can only ping things within the local subnet. If LE works when the router configuration is rather points the finger at the router being the issue is (which isn't our domain of expertise) not LE.
My personal preference has always been to aim for the least number of boxes vs. trying to eek out value in old purchases. I'd get the new expensive single-box VDSL+ router and eBay the old one to partially offset the cost.