No type experience and extreme reluctance to 'unpick' an excellent piece of flying from the benefit of my armchair in a situation I would have dreaded to find myself. However, since you have asked, my take:-
Yes, speedbrake would have helped dissipate the excess energy
I suspect it was 'stowed' for 2 reasons:-
1) We do not practice flaring and touching down with them deployed, so that would be an 'unknown', and the potential sink rates, possible change in pitch response and the buffet would have been dramatic and possibly disconcerting
2) It is driven into us that speedbrake must not be deployed below 1000', and with everything else they were handling at that time, it could have been an 'automatic' understandable reaction.