Well, I have never played the demo, but you might want to watch the commented Let's Play made by HitodamaKyrie on YouTube. It should give you some insight on how Nexus is really played.
Anyway, this game truly has a some learning curve, but I would compare it to Homeworld (oh boy, what trouble I had with that 3D movement feature...). Anyway, you can select any waypoint you want by keeping Shift pressed and moving the mouse (I think it was moving the mouse with pressed left button, but I don't remember exactly). This sets the distance, and then you only click on the screen to set the waypoint.
This might sound confusing, but English is not my native language, so plz bear with me. It will take some getting used to, but you will get it soon enough.
As for the constant movement, you have a button on the bottom of the screen (I think it was F1) where you can give the Full Stop order. I remember that Homeworld has a similar feature.
Anyway, take your time to get to know the game, and you will be greatly rewarded.