regarding unarmed damage: as mentioned before, the correct answer is no.
however, there is one exception: if your DM is using the defensive roll alternate AC rule from UA, wherein every time you are attacked, instead of adding the flat default 10 to AC, you roll a d20 and add that to your AC instead; this makes combat itself a series of opposed rolls (with a size modifier) - which would then qualify powerful build to affect combat attack and defense rolls.