you really dont need a wake to do a nose stab... I dont ski anymore since I got out of it 2 years ago but nose stabs were one of my favorite things to do.... try and do them
without a wake.....it will be much easier and faster to practice not having to worry about a wake... also try and get out when it is fairly calm if possible so you dont have to worry about anything but you and the ski. You are prob. trying to muscle things around and lifting your legs up too much or something.... try going straight at about 3/4 throttle for a little bit then start turning right so that the nose just barely goes right.... then punch it and crank the bars all the way left.... it takes a lot of tries so do not get discouraged if you dont get it right away.... it took weeks to learn for me and hours each day on the weekends... you have to let the ski do most of the work... figure out the steering and timing.... your body should kinda just follow the flow of the ski.... just keep an athletic type stance with both feet in the footholds... remember though that you need a little speed going into it... too slow or too fast not good... you will find the right amount after trial and error