HI Katie! You picked a great first race to do at Disney World. The Tower of Terror 10-Miler is going to be a blast! Of course, I think that all Disney races are great, but I especially love racing at night.
As you said, they have not finalized and released the exact course, but overall the Disney races are pretty flat. There will be a couple of winding inclines as you "exit and enter" onto the the highway parts, but mostly, it will be relatively flat. My favorite parts of the races are when you are running inside the parks and I think there will be a significant portion of the race inside of Hollywood Studios.
If your husband would like to attend the after-party with you, then he will have to buy a ticket. The party is included in race fees, but all non-runners need a separate ticket. You can
purchase tickets for the Disney Villains Hollywood Bash through the runDisney website. I definitely think he should buy one and join you in your celebration as you get your first runDisney medal! I am going to bet that it will be the first of many!!
I hope this helps. Please let me know if you have any other questions leading up to the race.