(4) is an incorrect application of modus tollens.

From ~s->(~p^~r), to get s by modus tollens, you need to have ~(~p^~r). Which rules of inference are you using? Can you use De Morgan's Law? Also, in (1), I think you mean, ~p v q, instead of ~q v p. And finally, in step 5, you seem to be compressing to steps into one.