The constant exclamations do sound annoying. It sounds like you've already tried to explain why you're not into Halloween, but maybe you could just try telling him, lightly but firmly, "Hon, I know you really love Halloween, and it makes me happy to see you so excited. But you know it's just not my bag, and it makes me feel bad when you bring it up. You know I'm happy to hand out candy and I love seeing the little ones' costumes, but I would really appreciate if you could limit the comments about my level of enthusiasm to, say, two a week. Thanks, and here's a bag of candy corn I picked up at the market today, they were having a sale!"
All spouses/partners have things that their partner isn't as into, as far as I can tell. BF is really into Dungeons and Dragons, he's a DM and loves putting his games together. I like roleplaying games and sometimes play, but I'm not nearly as into it as he is. Conversely, I love horseback riding. It's not his thing (he's actually never been on a horse before he met me) but he'll go riding with me when I get a chance, and he enjoys it. It sounds like the OP isn't pooh-poohing her husband's enjoyment of Halloween, and is in fact participating, just not at the level of excitement that her DH would like. She needs to have a little talk with him about how his behavior is affecting her, and hopefully he'll understand.