Looking Good Bud
Never would have thought of using a washer drum for a charcoal basket. As for holes I would probably make some a little bigger for better air flow and to let the ash drop out easier so you fire don't get choked out.
Cutting the top off might not be a bad idea so that the heat is dispersed wider rather than being concentrated toward the middle.
Looking forward to seeing the rest of your build and the first cook.
Good Luck Bud