D.S.
sounds so familiar. quit pushing if you want them to accept you this is normal step kid behavior. they all do this. I also went through the "my mommy says I don't have to listen to you " also. but they were 14 and 16 at the time. my response was (what my dad used to say oh I am turning into my dad scary) as long as your in my house you do have to follow my rules. The one thing I did to make them start listening but my step kids were old enough to do this with they asked when supper was my response was if you don't have to do your chores I don't have to do mine fix your own dinner. Your response has to be age appropriate though.
They are seeing it as you are the reason mommy and daddy aren't getting back together. as logical adults we know this isn't going to happen. they don't. If they don't pick up their toys put their toys in a trash bag and stash them away. When they tell daddy have daddy tell them well you should have done what you were told and this wouldn't have happened.
When mine refused to clean up after themselves and chose to treat me like a maid (remeber the age diffrence though) I sent them out of the house so I could clean up their messes. I cleaned it up and dumped it on thier bed dirty dishes and all. (alot of parents won't agree with this) So they had to pick up thier stuff so they could go to bed. after that I never had to tell them to pick up anything or do chores it was done before i asked. just remeber the age diffrence here. It has to be age appropriate.
This too shall pass and this is normal it is thier daddy and they see you as interefering with their time. just back off they will eventually start wanting your attention.treat them like you would your own they will come around.