Some success, got the mixture lever to behave. Found out by accident that if I push the lever most of the way forward then go to assign it, then I get the proper Axis with the reverse option and the slider even with the prop axis assigned.
Still absolutely nothing I can do with the Prop axis though. Nothing I do will change it from how it appears above. No reverse option, no slider. And in cockpit moving the Prop lever gives me only 50% or 100%, nothing else.