Ok... My take on this....
When we are talking about a max energy stop, then reverse thrust will not contribute significantly to the landing distance on a dry runway. On a wet then contaminated runway, then the contribution becomes proportionately much higher...
Short turnaround... Tend to use autobrakes off and 'Normal reverse' till we are around 60kt and then follow through with the brakes to a taxi speed. So question is in that case, what percentage of braking is done with reverse? I would suggest quite a bit. I don't think you can ever put a generic figure on it, because it so depends on the piloting technique used, the slope of the runway, wind component, weight etc.