Congrats on your contract.
I know you mentioned "talking" to the fire marshal but you really need them to come out and "physically see" the place. Walk thru the building with them and express your ideas of what your plans are. What looks good on paper can sometimes be a total surprise in person (this goes for any inspectors). Get aquainted with them and show you're there for them. You inviting them out before even getting started will show them you are serious AND concerned of doing it right and to their specs. Then after the build, reinvite them to come visit. Believe me, it will make a difference. Inspectors are the best friends to have
I owned a dark ride and had the "amusement inspectors" (Dept of Labor). If you do choose something in the amusement industry, keep all parties (inspectors) informed. For me, the amusement inspectors were easy to work with, if you get with them early, not just after you did something.
For the most part, if you keep the inspectors/marshalls involved with everything "from the start", you will be surprised how much easier life can be.
Good luck with your haunt.