Hi,
If you want your clients on eth1 to get IPv6 addresses via SLAAC then you'll need to enable IPv6 router advertisement with set interfaces switch switch0 ipv6 router-advert command.
Do you know if your ISP assigns a Global Unicast Address (GUA) on the WAN or do they use Link Local addresses? My ISP uses link local and I needed to add set interfaces ethernet eth0 dhcpv6-pd prefix-only to stop the CPU hitting 100% as reported in IPv6 processes using 100% CPU.
Do you see anything with show ipv6 routes?
Regards