when you moved them out try testingcheat and shift click on the house then object delete see if it will delete it. or call fire fighter if the fire is causing deaths then the fire is there so the firefighter shold put it out. if you have moved them out of the house you should beable to edit town from there new house, i know you can't if there on the lot the fires on cause it says you can't edit town while there a fire on lot.
if you use mods there allways twallan super computer this can be set for moving sims to another home without editing town, there a add sims , you can click your family then add them to another lot then edit town and delete the lot. or you can switch to another household in game then edit town evict the sims and then delete the lot.