Hi - my name is XXXXX XXXXX I'm a Family Law litigation attorney. Thanks for your question ~ no apologies necessary; I really appreciate the details.
The BIGGEST issue is to make clear who actually owns the corner cabinet. If your husband purchased the cabinet 40 years ago, then it is in all likelihood HIS cabinet, and if that is the case, then he's got the absolute right to do whatever he wishes with it - - including giving it to his daughter. On the other hand, if the corner cabinet was owned by your husband's deceased wife, then her ownership interest would have been either (a) willed to someone (if she had a will), or (b) transferred to next of kin under the laws of intestate succession (no will) - - in this scenario, it would be most likely that your husband and his children all have an interest in the item.
It would be best if your husband were to claim the item is his, that he bought it years ago, etc. - - because that would avoid having to deal with the interest of his deceased wife.....
Thus, your husband can take legal action to recover his property. He could file criminal charges against the daughter in law for theft, but that's probably not the route he wants to go.
The alternative would be to file a lawsuit in civil court and sue for trespass to chattles (personal property) and conversion (someone is allowed to use another's property and then refuses to give it back - - the person "converts" the item to his/her own use). Your husband would have to claim that the cabinet belongs to him and that she took the item without permission; he should be able to obtain an order directing her to return the item.
I know either way is a bit of a hassle because courts have to be involved, but if the daughter in law will not comply with your husband's request, that's really the only option.
I hope this answered your question, but if you need something else please let me know and I'll be glad to respond.