Maybe try some more troubleshooting on GrapheneOS? Also, I'm sure that the folks in the GrapheneOS Matrix channel are ready to help you out. You should be able to get Android Auto to work somehow.
Regarding AFWall+, do you actually need it? GrapheneOS has a built-in firewall, doesn't that work well enough for you? And can't you use something like NextDNS instead of AdAway? Also, the Graphene folks might be able to help troubleshoot the AdAway problem.
If you are going to switch to another OS, I recommend DivestOS. It's the only thing that even comes close to Graphene in terms of security. It's based on LineageOS, but has some significant security improvements, and for example allows for bootloader relocking. It's the only other OS recommended by the Graphene devs.