I use this script a lot so I was bummed when it broke.
I'm not really a mac scripter so I'm flailing around a bit looking for options. Here's one path for a fix that I've been playing around with: If you go to the Dock and Menu Bar system pref, and then choose Do Not Disturb in the sidebar, you can set it so that the DND icon appears in the menubar when DND is active. Then, you can access that menubar item via Applescript UI scripting. So, that's a hacky way to check DND status.
A couple of other things I notice, but don't really know what to do with. There's a Control Center app. Is that new? I don't know if that offers any solutions. Also there's a com.apple.controlcenter.*.plist.