How to Remote into my Mac Mini Server from Outside my Network?
Port forwarding examples:

When you set port-forwarding on your router, you pick a port number (or range of ports) and a single local IP address, ie. port 5900 and Ip address 192.168.0.2. So any internet traffic coming in on port 5900 gets sent directly to the computer on the IP address 192.168.0.2.


Answered above, you've specified one of the IP addresses in the port forwarding. It will be the IP address you specified in the DHCP address reservations.
It's only as secure as your password. I'm sure that the password is encrypted before transmission back to your Macs.


You need to set up port forwarding in your Router.

Depending on your Router's make/model, the setup may vary, but the basics are the same regardless.

I would choose a port way north of 1 or 2.

Both computers will be listening on port 5900, so you'd set something up like:

85.85.85.85:15000 --> 192.168.0.99:5900

and

85.85.85.85:16000 --> 192.168.0.100:5900