Re RTOW charts
TMAX is the maximum OAT certified for take-off, ensuring that the MCT limit is not exceeded. The value reduces as pressure altitude increases. (ie is not aerodrome/field specific!)
TMAXFLEX is the maximum usable flex temperature, when actual thrust is 75% of the rated take-off thrust.
It would be good if TMAXFLEX were indicated on the chart in some way but I think you can easily calculate it can't you? - it is ISA + 40°C.