I have a pfsense on VM on proxmix hetzner host, I dont route ip's from it though but use NAT instead.
However I can tell you I dont have any ip route in the interfaces file for the pfsense ip.
So the setup is something like this.
vmbr0 is the wan switch. physical wan is connected to it.
So no need for proxmox to route ip's for guests.
So remove the ip route commands.
Put on the 178 * 79 ip on pfsense, and use the hetzner assigned gateway ip for it, make sure this is connected to vmbr0, this should be enough to get pfsense internet access.
I have never done a routable wan ip setup behind pfsense for ipv4 though, so needs someone else to chime in for that, but I dont think they should be routed on proxmox either. Hopefully someone can help you on that step.
update
I had a look at this.
https://docs.netgate.com/pfsense/en/latest/book/routing/routing-public-ip-addresses.html
So I would try this.
Add a 2nd virtual nic to pfsense, connect it to vmbr0.
Add the first routable ip to the 2nd nic, set no gateway.
follow rest of guide.