I was concerned about the leap in the viola part too, however I was afraid if I doubled the cello (albeit an octave higher), the D would have been too strong (the D is already doubled an octave lower via pizz. bass). Also, throughout measures 1 and 2 the viola was playing the sustained piano part, but divisi so as to not be as strong. On m3, however, the E required equal power to the G# and B above it, requiring the full section. This meant the viola had to go from divisi in m2 to unisoni in m3. Would it have been better had the viola remained divisi, both playing the E in octaves?
As for the sustained D in the m1 of the viola part, the chord (as I analyzed it) was Cadd2. Yes, the piano arpegiated it, however the chord still needed the D.