From whom are you receiving your information about the Buyer's ability to close the transaction?
You write you're nearly 6 weeks past your closing date, yet the Buyer's loan has been in underwriting just over 2 (weeks). If your timing is correct, there was "never" a chance of closing on time!
What is your agent saying? What is the Buyer's agent saying? What is the loan officer of the Buyer saying? It makes no sense that no one knows anything and no remedy has been proposed. I will assume you are a FSBO - and if not, suggest calling a meeting with your agent and their Broker!
"Is there anything we can do...?"
The question is what do you "want" to do, and the power you have to bring that to reality. Can you push Wells Fargo to a decision? In my opinion, it's doubtful - but calls to the loan officer, their supervisor, and branch manager may help.
If you're a FSBO you have the Buyer's contact info. Call them. Over and over and over again. The responsibility to obtain financing is theirs, not yours.
If you are considering cancellation of your agreement, I recommend you have an attorney review your original contract and subsequent addenda so you can make a "clean" getaway.
You have the patience of a saint! Best of luck!!