I guess we should probably mve this to a git repo.... but oh well,
This version uses a ui.TextField -- editable text -- and sliders for size and weight. Then it dynamically gets CTFonts as the sliders move. I was worried this would be too slow to do in realtime, but it seems ok. fonts dont get technically get animated, but the steps seem fine enough that the effect is smooth. I wouldnt be surprised if this code leaks CTfontRefs, but things seem okay after a long time of playing with the sliders, so should be good for casual use.
BTW your PanVaria M and N seem to have issues.