FRL metric questions

Today, I use FRL as a heuristic to approximate the chance of a golfer achieving ‘low round’ in rounds 1 & 2. I’m wondering if there is a logical way to extrapolate this beyond the cut to rounds 3 & 4?

I was also wondering if Thursday Wave is accounted for within FRL implied probabilities?

Yes, FRL probabilities come from the same model as everything else, so weather/wave splits are accounted for.