If there is anything in the ip6tables information that you posted that would keep your router from processing LAN to WAN IPv6 traffic, I don't see it; but perhaps someone with a keener eye (and more IPv6 experience)* will look at it and let you know definitively.
*When I was actively providing network support before my retirement last year, I did not get involved with native IPv6 support because none of the ISPs I worked with offered it (and I did not even have any clients who needed/used IPv6 tunnels). I have therefore only been involved with my own IPv6 connections, and I have had to learn what I know about IPv6 the hard way.
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