You're running a PD client which will automatically configure radvd on your vif interfaces - your posted config looked ok in that respect. I'd remove any manual ra configs as they'll fight with the PD (and reboot the erl as sometimes changes don't seem to fully take effect).
Easiest way to check that link local address would be to ping it and unplug the wan router.
Given that you can ping from the erl I'd move to one of your clients and check what default route it has - it should be the link-local of the appropriate vif interface.
