Going from 30 minutes on the highest setting to 15 minutes on the lowest setting in two weeks is rather quick.
When I was pumping - I was pumping 20 minutes every 3-4 hours, except at night time. It took me almost two months to completely wean.
I never changed the settings on my machine when weaning.
Maybe try 15 minutes on the highest setting?
I mean - no offense... but no wonder you are having plugged milk ducts...
(P.S. Trust me - I know what a PAIN it is to pump all the time and I know how much you want to be done with it!!