Hi, i am new here but i try to help,
for ssh, if you don't have an option for the port in the web ui, telnet the router ip and setup dropbear
openwrt uses UCI to manage configurations, so likely, change the dropbear UCI config file:
root@OpenWrt:/etc/config# cat dropbear
option PasswordAuth 'on'
option Port '22'
22 to the port you want, then save and reboot.
To allow only some ip to connect, that's something related to firewalling, look if you have some web ui page for this, or study