I'd find a good tax attorney. Not the local H&R Block popup office. Would be worth a couple of hundred bucks for a consultation.
There are still ways to hide 2015 income, for instance with an IRA (until April 15th). You still need to find some money for the IRA, but at least you get to keep it for yourself instead of handing it over to Uncle Sam.
Good luck.
I am taking some offense from your put-down. I and many HRB employees have many years of experience and training. I am an Enrolled Agent as are many others at HRB. As in EVERY enterprise you can find competent and incompetent workers. At HRB, you can sit for a full run of tax situation and a bottom line with costs and then say "No thank you" and leave.
I do agree that he needs outside help. If he wants to spend a little time, call a HRB Office and ask for an appointment with an EA or Master Tax Advisor. It only costs a commitment of time. Try a tax attorney and you are committed to a likely minimum bill of that couple of hundred bucks just for the meeting.