Re: sad mac
Dude - go buy Synergy. Its absolutely gomsaggingly essential in your situation.
You have one keyboard and mouse on the master, and the other machines have theirs removed or shoved around the back.
All the clients simply look to the master for K+M inputs, and you move your mouse cursor from screen to screen just like normal. I run 2 clients and a master at work, and it support a lot more. Of course you can't drag windows from one machine to another, but you can (mostly) copy and paste data in the clipboard between machines. And if the master or clients have multimonitors of their own, that works great too.
Its so simple its utterly forgettable. https://symless.com/synergy
(Just a user, no connection)