install package from nethserver-testing repository and follow the "Current implementation configuration"
there is port 222 in the example to show how to change ssh port, but default is 22. You can skip that config setprop. I'll try to write it better on doc
how often? Now syncing is every 15 minutes. You can change it with a template custom of this https://github.com/NethServer/nethserver-hotsync/blob/master/root/etc/e-smith/templates/etc/cron.d/hotsync/10hotsync
But keep in mind that a mysqldump is done every time, if you have a big mysql database it is time consuming.
If your important data are on mysql and you whant to have a fast sync of it, or if you have a huge mysql db, I suggest to disable mysql syncing at all and setup a mysql clustering
BTW, it's safe to use short time, since there's a lock that prevent to run more instances at the same time
Yes: promoting a slave to master consist of a configuration-backup restore. If you have more than one network interface, you are prompted to chose which network assign to each network device. If you have one, IP is automatically assigned