What Metrics Tell Me Whether a Page Is Actually Easy to Use?

I want to measure how easy our support center page is to use, but I’m overwhelmed by the number of available metrics. Task success rate, time on task, error rate, System Usability Scale, and Net Promoter Score all sound relevant, yet I’m not sure which ones matter most for a content-heavy page where users are searching for answers. If someone finds an article quickly, does that mean the page is usable even if they spend a long time reading? Should I track whether they refine their search query or click the back button? I’d also like to understand how to combine quantitative numbers with qualitative comments without letting one distort the other. What’s a realistic set of metrics for a small team with limited time? Please share how you prioritize measurements and what thresholds you use to decide whether a result indicates a genuine usability problem worth fixing.