I know this is salesy, but you need to have a tool that monitors all this for you, using both Lighthouse (like you just did), but also RUM and CrUX data. Once you have that in place, you can establish a baseline of the current performance, and then gradually improve it.

Lighthouse is a lab tool so you can't rely on it for real-world performance. Let me recommend PageVitals (https://pagevitals.com) - i'm the founder - which gives you continuous Lighthouse, RUM and CrUX monitoring and alerting.