Why won't an NPC go into his house?
Solution 1:
If your demolitionist has claimed a room offscreen, you may need to go far enough away that he teleports 'home'. He's not going anywhere because he can't reach his house in the first place.
Solution 2:
Kill demolitionist with lava. Then he will respawn after some time. And maybe he will choose more desirable place :-)
When NPC begin to live in house not suited for him, I kill NPC and destroy chair and table. And in next time NPC chooses another house :-) After that I place taken off object on their place.
P.S. Magma is a solution for every problem :-)