Steely,
My younger difficult child has been oppositional 24/7 for about three years straight. This includes consistent lying.
We're to the point where we just hold the line with consequences appropriate for the situation, ex. limit or remove cell phone. We have not yet found a carrot that works. He seems content with subsistence living (meaning no privileges). If he earns a privilege back, ie. cell phone, he will simply abuse the privilege again.
So --- I've got to the point where if I can enjoy something with him, I will do it. For instance, I might invite him to watch a TV show we both like (even if has no TV privs we can still enjoy some time together watching The Walking Dead). We have a good time doing this. After The Walking Dead is over, he will immediately resume the ODD behavior (using the term ODD loosely as you know).
It's tough. And exhausting -- I just nursed myself out of a little depression and am trying to take care of myself. I hold the line and try not to think about it.
What's helpful to me is to laugh really hard every day. There is a show on Netflix now called Til Death about newlyweds who move in next door to a couple who's been married 30 years. It's a hoot.
Also I keep a gratitude journal at night which asks me to
~evaluate my happiness on a scale from "not at all" to "very happy"
~express gratitude for something that happened that day
~asks me if I have been in touch with friends
~asks if I have done an act of kindness
~ then write some kind of "happy note," not sure what that means but I improvise.
It sounds ridiculous but it is quite a little mood-lifter. An ODD person can be quite demoralizing.
Jo xxoo