Build up your shoulder and get a coat that has a high collar that you can turn up, you just need it to cover up the top of your head, use a scarf to hide anything else, placing spots where you can see of course, a black character hood should work. for you jack-o-lantern head. I would try and sculpt it. reference season 2 OZ episode of Face Off, to get some cool ideas for the pumpkin sculpt. with a costume this cool having a pumpkin you just throw away at the end of the night i think would be a waste if you going to spend so much time on a costume it should be one you can put on a display.