I've finished this now (needed 3 pints of dark winter ale to dull the pain of it) but am unsure of two solutions:
4dn. Year 21 maybe A_A_H_E - I assume this is Apache but t can't see why.
35ac. Wander aimlessly around Madagascar _O_M_N - I assume this is Mormon but can't account for the RM.
I really hope that other solvers find this crossword more fun than I did....