The flight was obvoius stable and therefore not stalling when the ACARS messages where sent. But the messages showed that the ADIRU and ISIS lost the airspeed information.
Wasn't said here, that ADIRU and ISIS had conflicting input, rather than total loss of input?
They where 3 houres in the flight. Therfore any overweight (which I highly doubt) at TO would not be an issue given the fuel allready burned.
A weight error would remain constant. It would be an issue for calculated max. altitude for the whole flight. How that could be practically relevant I don't know.