Lifting a leg on cue is definitely a prerequisite of the Jambette. So you are probably on the right track
As the Jambette is a behaviour that horses love to show, even unasked, I find it very helpful to have a clear cue for it. I would try to distinguish it as best as possible from other cues. Especially lifting a leg for picking hooves. So be sure you are facing forward when cueing for the Jambette, if you are not already doing so.
Your horse seems to be digging in his already learned repertoire of giving hooves and pawing to guess what it might be you're looking for. That's great. Now basically you just have to be precise in what you reward and what not. Are you using clicker training, by the way? I don't remember if you said so already...
If you reward only the small approximations that lead to the Jambette, your horse will soon know what you want. Look for every forward and upward motion, every stretch of the leg and reward. But right now, lifting the leg is fine. I would just ignore the pawing - it will stop eventually.