To make sure you do not break the wingnuts, freezing them in place, use
your homemade or bought tool to remove both nuts, lapping them into
place as you go with some silicon carbide "Clover" or equivalent
grease-mixed compound. _Don't_ just unscrew them; they will jam
eventually, and you will break a wing. Rather, loosen and tighten
alternately, working the compound in, preventing the buildup of tension
that will break the nut. A lot like using a tap, loosen some, then
retighten, never simply run it all the way out.

I agree they are made to be tightened by hand and should be
reconditioned until they do tighten by hand. Simply forcing them will
end up with a broken nut, and a non-adjustable adjustment.

Once free of the screw, they will be worn and loose but can be
replaced. If the new nuts are tight, then lap them into place, as well,
until they work smoothly. A thread resizing die can be used if you have
removed all the compound. If not, you'll ruin the die.