Overall Rating: 4.5 (of 5)
So, let's look at the first 5 measures. Our main chord for the first 3 measures is a Cm7. The Dm7 is thrown in just for interest, but the overall feel is Cm7. In measure 5 we know we're going to the IV chord (the Fm7), so we use its related V7 (C7) in measure 4 to make a stronger entrance into the Fm7. As far as the choice of a C7b9, the main thing is that our target chord, Fm7, is minor, so good tensions to use for this are b9 and b13. We could have just as easily chosen a C7b13 or a C7b9b13 for measure 4.
For scale choices, the first three measures all scream C dorian (C, D, Eb, F, G, A, Bb). The occassional B is in there just to imply a V-I cadence in C minor. When we get to the C7b9, we simply use an arpeggio containing the chord tones (E, G, Bb, Db, C).