Living by the words of the Bible

We have been doing our own family devotional every Sunday night and trying to get points across to our 12 year old.  I usually pick out the scripture or lesson and it comes from an email I get called Family Devotional most of the time.  http://www.worldbiblesociety.org/
These always have a lesson about respect or ignorance or something with a bible story and prayers.  I usually pick out ones that will make our 12 year old think about how he has been acting and possibly change it.  It has not seemed to work, because he still will come begging for something that he wants or being selfish.  We read one the other day saying that people are to absorbed with material possessions and to think of others instead of himself.  It did not work, he still is always begging for something that he wants.  We try to teach him that if he wants something that he should save his money up, but instead he is constantly wanting to run to the gas station down the street to buy snacks and wasting his money.  It is so hard to teach a 12 year old something when he was raised differently by his mother and he is at the age that he thinks he is right about everything and us as parents are unfair and don't know anything.
He has been very spoiled by his grandmother and thinks he deserves all the expensive electronics that we can't afford but she buys him.  He doesn't appreciate them, because he ends up breaking them within a month and then she just buys him another one.  I have tried to get BB to make him save his money to teach him but he doesn't do it.  A lot of the time his excuse about stuff is that he it is too late to change him his mother already did the damage.  I tell him that it is never too late to teach him a better way to do things.
 Just like when he does not agree with the music he listens to or some of the shows he watches, he still lets him listen and watch them because he says his mother has done the damage and it's too late now.  That is absolutely not true, he can make him stop listening and watching inappropriate stuff and explain to him that it is language and actions that he doesn't think a 12 year old should be listening and watching. Some of the things he thinks are ok or I'm just being way to worrisome or protective about them, I tell him that is just how women are.  But usually we end up fighting about the fact that some ways we think about raising children are so different.  I believe that a lot of the time the reason the 12 year old doesn't respect me or listen to anything I say is because his father gives him the impression that I don't know anything and he doesn't have to listen to what I say.  That concept is so wrong, we try to tell him that he should always be respectful towards adults and do what they say especially his father and I.