As far as getting lead change for the hind end when you ask for the change try to scoop him up under himself. I like to imagine that I'm somewhat scooping up ice cream and do a little of that same motion with my hands. I hope this helps!!!
What I usually do is I change directions over a pole at first and if they don’t get the lead change I circle them over a pole a few times to give them a chance to understand what im asking them to do. If that doesn’t work I do a simple lead change and start over. I find that repetition helps my horse figure out what cues mean what.
Going throught your changes but using ground poles to let them change their lead over. Dont get frustrated they wont get it right a way it will definitely take a couple tries or more, its just a learning process