Mac – Remote SSH access to sleeping MacBook Pro only works when ‘Find the Mac’ application is running – can I make this persist

For keeping the connection alive, you can check in /etc/ssh/ssh_config the line where it says ServerAliveInterval, that tells you how often (in seconds) your computer is gonna send a null packet to keep the connection alive. If you have a 0 in there that indicates that your computer is not trying to keep the connection alive (it is disabled), otherwise it tells you how often (in seconds) it is sending the aforementioned packet. Try putting in 120 or 240, if it is still killing your connection, you can go lower, maybe to 5, if with that number it doesn't happen, maybe it is your router who is dumping the connection to free memory.

For killing it when it gets hang up, you can use the ssh escape character:

~.

That is, press the tilde and then the period, if it doesn't work, press Enter before you press that, that will kill the connection immediately.

A lack of wake reason entries suggests your Mac is never fully sleeping. The sleep mechanism has started but never completes.

Use the following Terminal command to view a detailed log showing your Mac's power history:

pmset -g log

You will see a list of entries in form:

 * Domain: applicationresponse.slowresponse
 - Message: PMConnection AirPort configd plug-in com.apple.powermanagement.applicationresponse.slowresponse 1399 ms
 - Time: 13/03/2012 12:27:53 CET 
 - Signature: AirPort configd plug-in
 - UUID: AB482838-2D6E-0000-0000-14BF53E20000
 - Result: Noop
 - Response time (ms): 1399

Look out for applications that may be keeping your Mac awake and active. Applications and other processes can keep your Mac awake if they are providing a service, such as file sharing or remote access. However, processes should be forced asleep after 30 seconds on lid close.

The behaviour you are seeing suggests a kernel extension or IOKit problem. User level processes can not block sleep when instigated by the user.

Do you have any utilities installed that install kernel extensions (kext)? These might include screen recording or audio capture tools; utilities than need low level access to your Mac.