Can I be charged with theft by deception for not returning rent-to-own merchandise?

From what you write, you have *not* committed theft by deception, or any kind of theft: you have taken or converted the furniture for you own use, but rather, apparently had the furniture available to be picked up, but the store/company refused to take it.

Possibly, they could consider that you have destroyed the furniture, if it is too infested by bedbugs to take back. If that is the case, then while you would seem to not be criminally liable, they could hold you accountable for the value of the furniture and sue you if you do not pay it voluntarily. You in turn might be able to sue the building or another tenant, if either is responsible for the infestation.