You step 8 is incorrect.
Here's how I would do it:
1. DvM
2. M-->R
3. Sv(Q&X)
4. R-->~S
5. ~D /Q
6. M 1,5 DS (disjunctive syllogism)
7. R 2,6 MP (modus ponens)
8. ~S 4,7 MP (modus ponens)
9. Q&X 3,8 DS (disjunctive syllogism)
10. Q 9,simp (simplification)
Edwin