Spouse has alzheimers; How to make the deal happen

[Duke George Brady]

I have a small parcel (market just under than 25K) I've been trying to figure out if I can move on, seller agreeable to ~5K.  

The wife wants to sell, and claims to have made multiple sales of their Joint Tenancy properties since her husband became incapacitated by his affliction.  He is in the "late stages" of the disease.  No Power of Attorney Exists, nor a will.  

Avoiding the hassle/time/money of Guardianship or Community Admin., I'm wondering if anyone has experience using a "Subject to Marketable Title" contract, and what that looks like.  I'm assuming the Title Co. won't insure it, however, without his ability to sign.  If seller is agreeable to an extended contract for several months, would this be my safest option?  Seems morbid to just wait out someone's illness like that, but don't know of another option short of a risky QCD.  

The wife is convinced it can go through without his signature, but I wonder if it's because her previous sales were just with Quitclaim deeds, where the buyers took on the risk knowing they are Joint Tenants, there's no will, and that his diagnosis is terminal.  She did sell a parcel for 100K to a wholesaler who didn't double close; she was not happy about seeing the 10K they made after selling for 110K. 

Creative suggestions?