Looks like you might have some stiff competition.
http://tv.yahoo.com/blogs/the-set/nbc-orders-munsters-reboot-pilot-165508698.html
I think this was mentioned once before but it's worth bearing in mind. While Dracula, Frankenstein, and generic 'creatures of the night' (mummies, devils, vampires and werewolves) are outside of copyright and potential trademark issues, I'm unsure about the Creature from the Black Lagoon. And with the re-make of the Munsters, NBC's lawyers will probably be on the lookout for potential conflicts. Yes, you're characters are differently named and act differently, which is to your benefit.
I don't wish to debate about whether screenwriters should or shouldn't concern themselves with writing with copyright in mind. For my part, I think screenwriters wishing to sell their work need to be attentive to potential conflicts while writing what is needed for their story. It's a trade-off. If you are shooting your own script, you will need to negotiate those rights, but it's your vision done your way. When writing on spec, it is sometimes better to err on the side of writing it less dependent on securing rights.
When you create this world, the audience is going to wonder how they survive day-to-day. The Munsters have this quasi-reality of fitting in (world of work & daily activities) albeit bizarrely. While you don't need to go into elaborate explanation, that needs to be shown so that the monsters can gather at a local dive, even if its only for monsters. How did they get there? Do they drive? How do they get drivers licenses? What do they drive? How do they get money to go to restaurants, buy cars, etc.?
I'm not suggesting you remove the diner scene, but you need to make it semi-plausible. Perhaps place it in an out of the way swamp. Have a brief flash of the outside with Norman and his wife getting off a horse-drawn buggy or something and cross a mist covered bridge to an old scraggly shack with a skull and sign that say "Kepe OUT!". Now flash to your inside dining room.
While I appreciate wanting to use the invisible couple, my gut instinct is that you already have enough characters. Less is better. You presently have 10 actors. Adding two more to your story doesn't add much value. Most shows have 6 central actors (2-3 main, 3-4 supporting) and a few auxilliary as needed. A comedy is usually spiraling, so you simply need to focus on your two main characters--Dracula and his wife. Each receives good (and bad) advice from the others.
If I'm writing for a webisode or TV, I know how many pages everything has to be. When I write a feature, I allow myself to be more creative. Since you want a feature, I would focus more on developing the story than worrying about its length. Once you're finished, then you can judge what needs to be adjusted. When a script is properly formatted (using CeltX, say), one page is roughly one minute of screen time.
When I share comments or examples, you're welcome to incorporate them in your work. At this point, I'd focus on the initial conflict. I sometimes "transplant" comedy casts in to see their reactions. How would the crew from "Gilligan Island" react? Or "Friends"? Or "Seinfeld"? Or "I Love Lucy"? etc. If you follow up on the ScreamFest idea, what might this Von Stumpf be like? How might he treat others, especially individuals he thinks are dressed up like monsters? It's okay if things get crazy because in the end, whether it comes together or falls apart, the real dynamic--the monsters and their wives appreciating each other and themselves--is what it's all about. That's what you really need to resolve. That's how I would approach this movie. Great movies are about the human dynamics (of course, special effects don't hurt).