Lets see if i can answer both of these.
The hall sensor has to be very close to the magnet and the movement is very small. It took a few prints to get this to work right.
I used these references which were very helpful
In my design the hall sensor sits in the square pocket in the blue part and the .375"diaX.50" magnet takes up the rectangular space (i used a cylindrical magnet, this is a cutaway view)
For the throttle friction I made a tapered & split thread on the bottom end. The nut can be tightened and it bends in the tabs. In hindsight it would have been better to make the nut tapered instead. The green collar prevents it from moving axially
