Prednisone is nasty but can be helpful. I have been started on various dosages at different times but I agree that 40 mg is an average starting dose and 60 mg and above is considered high. The most common taper schedule was reducing it by 5 to 10 mg every week or every 5 days. So 3 weeks for 40 mg is pretty fast but not outlandish.
My side effects were weight gain (about 20 lbs), mood swings and having a huge appetite. I also was very unstable emotionally. I would go from euphoric to feeling like crying very quickly. The good news is that the side effects are temporary.
Good luck. Pred helped me in the early years of UC, not in the later ones.
MyUC