Having done a previous Windshear go-around, and I suspect with the Windshear escape manoeuvre in his mind the captain (or FO - we don't know if he advanced the thrust levers further as part of "set go around thrust") made an error typical of those made by a fatigued pilot in applying parts of the wrong procedure.
Very possible. I think the data plots would help because we don't know the max pitch attitude achieved. If it is very high then the stab trim input may have been intentional for the whole 12 seconds, ie he kept running it until the nose got back to 15 degrees and by then it was too late as a rapid pitch down was inevitable.