You can have your macro Pause for 130*60 seconds, and then do whatever you need to do to stop the recording.
Note that with any long running macro, there is the risk that you might restart your Mac, sleep your Mac, quit or relaunch Keyboard Maestro Engine, etc. I don’t expect this would be a problem in this case, but it is good to keep in mind any time you consider a long running macro as a solution to a problem.
If you go to your Preferences (click your profile icon at the top right of the forum), you can adjust when you will receive an email. “Send me an email when someone quotes me, replies to my post, or mentions my @username”.
As you worked out, you can select a macro or macro actions and choose Edit ➤ Copy as Image, and then you can post the image in a topic using the Upload button (which has a shortcut of Command-G on a Mac). There is a macro that can automate most of this process at the topic Select Clipboard Image File.