Point A I don't understand, because if we do an RTO the speedbrake already has to be raised manually in accordance with Boeing procedures. So why are we more limited on the Takeoff field length weight and brake energy limit weight
From the FCOM:
If the SPEED BRAKE lever is in the DOWN position during landing or rejected
takeoff, the auto speed brake system operates when these conditions occur:
• main landing gear wheels spin up (more than 60 kts)
• both thrust levers are retarded to IDLE
• reverse thrust levers are positioned for reverse thrust
So yes the Boeing RTO procedure is a backup for the automatic procedure.