Another small issue is the augmented second I see in the bass of the third measure of your third exercise: the line moves from Ab to B. If the lower parts are not melodic and only serve to paint a rich harmonic accompaniment, chances are the ear will not notice the awkward melodic interval. If, however, you are writing vocal music or mean the part with the augmented second to be a melody, be sure you realize what you are doing.
The augmented second is often found melodically when arpeggiating through a diminished seventh chord or in between statements of a short motive. Only rarely is it appropriate in the middle of a continuous melody, perhaps as a special device. Otherwise it acts like a large leap, splitting the line in two or even worse, just sounding awkward.
Thus in a
harmonic texture like yours it is fine. Once again I was just not sure if you were fully aware of it here.
And I found a good quote!:
Kostka, Stefan and Dorothy Payne (2003).
Tonal Harmony, p.289. "The line between modulation and tonicization... is not clearly defined in tonal music, nor is it meant to be."
