@redrobin089 Specifically, go to Edit Town, click on the family, click the Split button, and split out the firefighter. He should now be on the clipboard, from where you can put him right back into his house. You could also try temporarily placing him in a different house, then moving him back in, while quitting to desktop and deleting the cache files in between. Be sure to use "save as" to rename the save in between, so you have a backup if this doesn't work.
You could also try using MasterController to reset the sim. Click on him and select NRaas > MC > Advanced > Reset Sim. This doesn't usually fix the walk style, but it may address other issues, which would then let you evict and replace the sim without breaking his data. Or DebugEnabler might work afterwards.