It seems your main problem is with dynamic prefix assignment by your ISP. With this alone it is hard todo what you want reliably. There’s 3 options you can opt for:-

1. Bug your ISP to hand you a static prefix. (/56, /60)

2. Use a tunnel broker(HENET)

3. Setup a Wireguard VPN on Linode and route that to your home. You get a fixed /56 from them.

Nothing else I can think of. Good luck.