I am assuming you believed at the time you talked to your xh that he would parent your child to the best of his ability, right? If so, if you love your ds15, let him be happy living w/his dad and using swear words as terms of endearment between them... He wasn't using them toward you, right?- knowing your views of such words differ from your xh's?
What evidence do you use to base this?
Quote: Everything i tried to instill in my son: work for what you want, treat people kindly, do good in school, be accountable for your actions seem to be thrown out the window.
I don't see anything in your post explaining that his grades have dropped living with his father, or behavior one could describe as "doing good in school," has been affected negatively by moving w/his dad. In fact, wasn't it going downhill before he left to go??? If it's no worse than it was, and he's happy, I would try to motivate him to do better from afar by offering any sort of carrot that might get him to move in the direction you prefer, but let your xh lead the guiding, and make sure he agrees that offering whatever carrot is a good thing, inyour child's best interst.
He's the one you ought to be talking to, find out what he thinks he's doing w/his system in place, what his goals are for your child and how they match your child's goals... kwim?