I had to purchase a key, it wouldn’t let me talk to the controller until I got a key, but I really don’t know. If you’re controlling it, then I guess it doesn’t need one. 
There are maximum setting in the controller are more like speed limits. You should be able to set the console the 5% and fire it from the console with the tube producing 5% out. However, mine won’t lase below around 8.8%.
Has this machine ever worked properly?
I don’t know about this setting, I have a Ruida controller, maybe one of the others can help you here.
There has been a few posts on problems like yours. Might want to browse them.
Here’s one of them Power Settings Won’t Adjust