Sometimes, asking something politely may not get though to them if your always polite to begin with. Maybe you need to be stern about it? He might see that your serious.
Instead of making this a long conversation here. Could you send me a message and I'll talk with you more that way?
I might, not sure but might have a few ideas.
if you have to ask him, you probably are past the politely stage.
remind him the arrangement was temporary so you would like to know when you're getting your couch back.