Love the costume and thats one of Howards best busts.
As a suggestion, why not make an alginate mold of your hands clenched in a fist then create a plaster plugs which you can then change or modify once thats perfect, create silicone molds from those which you can knock out urethine resin copies... long process but it'll make a massive difference. Not sure but you might also be able to track down better hands on ebay