I've played this sonata! Did it a little over a year ago. Lightness of touch for those ornaments is a must. Practice the ornaments very slowly, but be very light with your touch and quickly flick your fingers back after each note. Like you've very quickly and lightly scratching each key. Obviously, you won't do this in performance, but it's a way to emphasize quickly coming off the key, and not putting too much weight on the note, which will slow you down. Once you get that down, speed the ornaments up a little bit, and don't do as much of the "scratching," but still focus on a lightness of touch while being even. Once you get that solid, try it at various faster tempos.
And use the pedal for each ornament, too.
Regarding the arpeggios in the development, you need a flexible wrist and good hand position. No extra tension, and a good transferring of arm weight through each finger. This would be difficult to explain on the board, so your teacher would be your best bet.
In the fourth movement, do you find the sixteenth note runs in the opening section awkward? I just had to do slow metronome practice and speed it up gradually until I was at full speed. Once again, good hand position is a must, or else you'll have a heck of a time getting it even.
