Pause detection in particular is tricky. First try if Google Home allows you to create a routine “when the media is paused” (that’s possible with some Chromecasts, maybe not with the Shield), and then you could turn on a virtual switch in SmartThings or just control the lights from said Google Home routine.
Even if there were no PAT limits, using an automation app like Tasker or Macrodroid would not be practical for the “pause” event. The way automation apps detect media pausing triggers even in very short video previews when they finish, it would be annoying to have lights going on and off all the time (you can always add more logic to automations so the pause action only runs if it’s been playing for more than X time to avoid short videos but feels cumbersome).
Talking about apps, Tasker has started testing with a plugin for Google Home API so it can switch on/off devices integrated into Google Home like, again, SmartThings devices or virtual switches. They also support Matter so, if they’re Matter lights, Tasker can turn them on or off from the automation (I haven’t tested that).
There are other alternatives like installing a server with Home Assistant. HA supports webhooks too (local, so they don’t need clouds) and, for the TV case in particular is probably better since it can receive the Google Cast notifications and those only happen with actual content and not previews.
Adding HA to the mix for an automation would be easy if the devices are Matter (since they support multi-admin) or have local integrations, that way they don’t depend on SmartThings integration at all.