What mixing ratio of ethanol and acetone has the lowest freezing point?
its me again, I  want to post the answer I found because I think it might be useful for somebody in the future; it appears a 2:3 molar acetone:methanol proportion gives the lowest freezing temperature ~158 K (see attached picture below).

It appears the difficulty finding these curves was because they are usually called "solid-liquid equilibrium" curves instead of "freezing point curves", as its the same physical situation (Explanation Here)

There is a large database of these in the following link.



EDIT: As commented by "Ivan Neretin", ethanol-acetone mixtures are also good for low freezing temperatures: