By the way, based on the info you have in your thread, I'd say the affair isn't over, so snoop carefully and don't get caught. This is not a sprint, this is a marathon. The strategy to finish the marathon is to be well prepared.
VAR, GPS and internet monitoring should get you info. If he doesn't suspect being monitored, he will not go underground. If he finds out you can monitor WiFi data, he will use mobile data. So set it up while you are all one. Don't use a shared profile on a shared pc for monitoring. Don't get caught.