You need to slim the arms by a great deal. The armor was made for very slender people. The length and proportions seem right, but the thickness of the upper and lower arms are way too much. You don't want arms that are bigger than the legs. Make things slimmer, but not as slim as the Kaiyodo sculpt, as those are basically as thin as regular human arms without armor and the Gentle Giant versions seems just a tad bit too thick... so somewhere in-between.
Always think slender when sculpting this piece.
I would pull up the tip of the right lower arm to just above horizontal level, or maybe, just below, depending on how you want him to hold the barrel of the blaster.
And then turn the tip of the left arm about 10 degrees in towards the right, if that's possible. I would also pull it up about ½ a centimeter at the elbow, as it's sitting a bit too low.