Hi! I have a few suggestions :
1. If you use a 9/8 indicator it has sound like that! Maybe, a bass that marks the three pulses (as in waltzes) would be a good a idea. [Check La Valse - Ravel: Holberg's Suite Sarabande- Grieg]
2. The tuning of keys in strings is different from pianos, in piano it doesn't matter if we are playing in C major or Eb minor because all sounds the same, but this is not true when we are speaking about strings. Violin has 4 strings: E, A, D, G; those strings sound more brilliant when they are not pressed, in Bb minor E, A and G are flattened so we use just pressed notes (i'm really trying to express myself in another language, i'm doing my best i swear, if you dont understand me pls tell me), that makes the sound more dark and weak (also its very hard to play correctly) [check edward grieg op. 27 no. 1, look that in the first chord a lot of notes are open strings][compare it with Tchaïkovski Op.48, no note is an open string and it sounds softer and weaker] Usually, string composers dont use more than 3 flats/sharps.
3. If you want a passage to sound 'violinesque' you have to use the E string, the second melody in bars 1 -7 (violin II) will sound better if it is played by a viola, as the violist will use the G string which is very present in viola repertoire and is characteristic of that instrument [check hindemith's viola sonatas]
4. b12-13, parallel octaves between db and viola, also, i miss the c in the bass
5. If you use a db, you have to use a cello, if not, the pitch of the instruments are not balanced.
6. To sound more impressionistic or more alike to debussy's music, avoid V-I progressions, also it sounds pretty contemporain (i dont know if thats intended, cool if thats the case) [check ravels mallarme poems, look at cadences] [check la fille aux cheveux de lin, b2-3, its a plagal cadence, b9-10, look at the V chord, it has no leading tone!]
I hope this helped you!
- Samuel