I have had similar issues with dp and dsc's.so cam sympathise but the other posters are right the issue is with dp not dss.
The key is that ur dss has had no discipline...prob as a result of the guilt dp feel for the breakup - regardless of whether his fault or not.
My dp had a major hangup about time with him being nice and fun and not about rows over behaviour. We had a lot of arguments going over the same thing...kids need boundaries and rules or thy run riot. It has taken a while but we are getting there.
It is vital that punishments are followed though and that you are both seen to putbup a united front....maybe get ur dp to watch a few episodes of supernanny?!