Another thing that can probably work is doing multiple (like >5) slightly basified (to ensure not losing DMT) water washes. When adding acetone to NP + water, acetone will go mostly (I don't know precisely how much, but like 65% or so) to the water. Some stays in the nonpolar, but repeatedly washing with water will remove most of the acetone from the NP.
When you have your NP separated, add water and shake thoroughly. Discard the water and repeat.
EDIT: I just realized that potentially you will still lose a bunch of DMT because the water you will be discarding now has acetone in it.
Another strategy may be to distill/cook the acetone out of the NP, if the NP has a significantly higher boiler point than acetone (56 C)? Be careful not to set the house on fire