for 1. check these options, I think that should do the trick:
man 5 sshd_config:
Sets the number of client alive messages (see below) which may be sent without sshd(8) receiving any messages back from
the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client,
terminating the session. It is important to note that the use of client alive messages is very different from
TCPKeepAlive (below). The client alive messages are sent through the encrypted channel and therefore will not be spoofa‐
ble. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The client alive mechanism is valuable when the
client or server depend on knowing when a connection has become inactive.
The default value is 3. If ClientAliveInterval (see below) is set to 15, and ClientAliveCountMax is left at the default,
unresponsive SSH clients will be disconnected after approximately 45 seconds. This option applies to protocol version 2
Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message
through the encrypted channel to request a response from the client. The default is 0, indicating that these messages
will not be sent to the client. This option applies to protocol version 2 only.
for 2. set
PermitRootLogin no; there are also other possible values:
Specifies whether root can log in using ssh(1). The argument must be “yes”, “without-password”, “forced-commands-only”,
or “no”. The default is “yes”.
If this option is set to “without-password”, password authentication is disabled for root.
If this option is set to “forced-commands-only”, root login with public key authentication will be allowed, but only if
the command option has been specified (which may be useful for taking remote backups even if root login is normally not
allowed). All other authentication methods are disabled for root.
If this option is set to “no”, root is not allowed to log in.
Right (from old answer as noticed in comments): You need to restart SSH daemon: