Selfhosted

You are running into the ultimate, and ultimately unavoidable, limitation of self-hosting, which is the self.

You should run a VM on the VPS for Vaultwarden, with no other services in the VM except whatever you need to connect to it remotely. Keep it simple. Run an exact copy of the VM on your local server. Have the VPS instance push its database to the local instance regularly, to keep up with any changes that your users make. Make regular backups of the local instance.

When you need to update the software, freeze an image of the local VM and then update the local VM, then when you're sure it's stable, copy the updated local VM to the VPS. If either the local or VPS instance crashes out, you should be able to recover (or reproduce) one from the other.

In the end though, it is functionally impossible to ensure reliability by yourself. Hosting Vaultwarden on a VPS shifts the responsibility for running the underlying server and network connection to the provider, and probably removing the dependence on your residential network connection will be better for your family/users.

You are still the weak point in your system. You need someone else who can log in to your local server, and into the VPS, and perform recovery if needed. There is no technical solution for this. You cannot be the sole admin, and also ensure reliability for other users.

A VPS is going to have all the same problems as a local server in terms of inexperienced users, and will also add all the extra hassle of managing and paying for the VPS account.

I would say the best options for emergency access are local backups and documentation, which you already have. You could also consider keeping additional copies of essential passwords (like email accounts etc) in a simpler vault like Keepass. Or even physical copies written down in a security envelope in a safe.

I have vaultwarden on my home server and I usually visit it through it's Webinterface because the bitwarden addon for my browser breaks all the time with my vaultwarden instance.

I also have tailscale and a Headscale server so access should be VPN level secure.

I'm gonna be honest, it's quite inconvenient sometimes but it's an ok working setup.

The addon issue gives me the most headaches because it means I have to login like 10 times into the web ui and then search through the passwords every time I am building stuff on my servers.