OK, here's a complete method. You might want to start over and make only these two mixes.
1) Normal Mix THR > THR at -100%, -100% offset -100%, switch ON. This disables the throttle stick and puts the default throttle at low.
2) Normal Mix RLv > THR at 100%, 100%, offset 0, switch H. This causes the Right Lever to control the throttle across its full range. Using switch H allows you to give control to the normal throttle system (which is locked in the off position because of the -100% offset) in one position, and to the slider in the other position.
Now you have disabled the throttle stick, enabled the H to serve as your throttle lock, and put the right lever in as the throttle control.
Andy