I would have a standalone Forgejo server to act as your infrastructure server. Make it separate from your production k8s/k3s environment.
If something knocks out your infrastructure Forgejo instance then your prod instance will continue to work. If something knocks out your prod, then your infrastructure instance is still there to pull on.
One of the reasons I suggest k8s/k3s if something happens k8s/k3s will try to automatically bring the broken node back online.
Both. Why have one account? This isn't Reddit. Having alts on other servers is fine as long as you don't vote manipulate or use it for ban evasion.