The auction (ebay noted earlier) ended at $36,300 so reserve must not have been met if the same seller (Beverly Hills Motor Car Club) has it on Hemmings at $75,000.
There is a Darrin division / chapter of the KFOCI I think and there are Darrin owners that come on here, such as Terry T.
Some folks don't like to hash out values on the forum. I would personally seek out Wayne Carini of "Chasing Classic Cars" fame and see if he can do a show on your car and get it at an important auction. That way you get to share your dad's story, move the car to a better home and get a good price for the car.
To me, there is not a lot of Darrin level money in the club. Meaning most of us don't have the cash laying around to make a reasonable $35,000 to $60,000 offer for your car. It sounds like even you would not be able to afford the car, if so inclined so that's not a slam, just a realistic reminder of the 1. the special rare air of a Darrin and 2. realities of most of our budgets.
From experience I can tell you that you should seek an auction result to put the car in the best place to be restored or stay in nice original condition because if the speculation market returns, and values for Darrins skyrocket, the buyer who buys it from you at less then market value for sentimental "club" reasons will at least consider quietly selling the car for the profit that would have been rightfully yours. Also, most folks in the club that can afford a Darrin are elderly and using retirement funds and the Darrin might end up in the same state as you are now, in another 10 years.
So, probably not great news, but cars like the Darrin are rare artifacts that like rare paintings have tremendous value as hedges against inflation and keeping cash laying around. I hope you find that rare KFOCI member that is young enough to own it for several years (20 +) has kids that will appreciate his old car collection and keep most intact, has the money to give you fair market value and will show the Darrin at National or Regional meets. That's a rare person, if one even exists.