statutory employee

First, read the definition of statutory employee. He is not one.

Second, do you know what code V is and how it pertains to him?

Third, if he is an employee he cannot deduct for a home office. Read about unreimbursed employee expenses 

So he got half a million in stock options, sell some of them and pay the taxes.

I'd sure like to restate or clarify some of this:

A W-2 doesn't take "all taxes out." It's a guesstimate based on the payroll form W4, which the taxpayer controls, as well as having the ability to pay Estimates when something unusual happens in the tax year, across their entire financial events for the tax year. Think of it as Prepayment; not Taxes. Seeing a taxable bonus or other condition at year end on his final paystub (where they put YTD) means he could have paid in an estimated amount by Jan 15, if needed. It seems unlikely this one event is the issue, though. More likely, this person's entire financial year is a bit complicated.

"Could he be a Statutory employee where all expenses could be utilized on an 8829?"

It's unlikely he has $55k of costs in the operation of being an expert medical witness. A lot of employees worked from home in 2020, unexpectedly. Congress has not yet made a change to the lost tax benefit in TCJA for costs incurred because of this condition.

The farm is its own issue. His labor as "extensive work" isn't of value by itself, since he is not his own employee on the farm. Working on your farm has an impact to the farm of increasing its bounty or value. If that is in preparation for a Sale, than costs for improvements should be tracked as part of basis. The costs for repairs would be on the farm schedule in his tax return. Have you done this part, yet? Or is this a hobby farm?