I appreciate the effort but this advice is not especially good.

For example fail2ban is fine but it's almost always better to just use ssh key pairs.

His firewall configuration doesn't do anything basically, just gives access to the network services that are already running, and logging firewall errors is only good if they are actionable (they rarely are) otherwise they are just filling up disk space.

The sysctl entries, I haven't checked one by one by the look like the defaults in a modern distro.