I agree with suggestions above to be open way more weekends. The first weekends will have a feel like what you just did but, it should be the word of mouth to multiply for the final weekend. A small town like yours can see 5,000 customers regularly.
I'm kind of guessing your building was originally Service Electric? If so I see a big opportunity where the back right side of the building might have the exterior all year long remain decorated as haunted house and be a billboard for the haunted event including dates for next year. The front of the building and all of the interior remains most of the time devoted to a more conservative spa business show room. People going down the road and shopping nearby have something to look at and wonder. Actually the front exterior never changes from advertising hot tubs and the haunt advertises that core business as well.
Like you say, some characters and some social networking and a little radio and you will have attendance way up there to begin with. Only doing one weekend will stay at 1/10th of your potential.
Also how much you charge is a big indicator to customers of how special an experience it might be. Is it a deal meal at burger king or Outback Steak house with the only difference realy being how much was spent on detailing. What you have doesn't look bad in the pictures. It is ind of like the old saying when someone is charging a lot for something, they must be proud of that. You should be proud and be compensated accordingly. In later years raising the prices may be a turn off. Only instead of upsetting only 1/100th of the population you are effecting 1/10th and their willingness to get off the couch. A little higher price is a bit more exciting.
I sold my haunt last year as the charity I supported decided to lower the price and be open less nights. It didn't seem to do what they expected it to. No one asked me before hand. I sold it to people that in their 3rd year are seeing well above 10% of the population and still increasing yearly. It is now their 2nd attraction in a town that was kind of lame with all sorts of events going on in October that would be competing for that same dollar.
Other keys to marketing become having lots of people a buzz with the doing detailing in the haunt and learning make up and actually qualifying to be an actor. They too see things and learn things they share with anyone they meet and that is better than spending thousands on advertising. It all becomes a serious process before hand where an investment was made in people. It takes time for everyone to be able to communicate to a number of people. You might be able to set the haunt up in a week but the educational process is weeks before that. Training the customers takes weeks also to see the fruits of everyone discussing what they saw and would do again.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.