MaxBlow
The reason why 'RTOLW charts are not limited by structual weight is for cases such as yours, where a performance decrement has to be applied. Even with your deficiency, the aircraft was still capable, from the performance stand-point, of takeoff in excess of the Structural Limit. It's a right pain in the butt when manufacturers cut off performance data at the Structural Limit because performance decrements then have to be applied to this limit.
Whilst it may seem a futile exercise to you in THIS case, I'm sure that if you scan through your RTOLWs that you'll find plenty of shorter runways etc. where a performance decrement would have lead to a RTOLW lower than Structural Limit.
Do the performance calculation with applicable adjustments, compare the result with the Structural Limit, and observe the lower.