Given the menuet feel this piece has, I'm not certain why you chose to put it in 3/8 rather than 3/4, but I'm sure there is a reason.

The introduction in the strings is fine; no qualms there. The piano arpeggios, especially without pedal, seem a little thin. I'd add pizzicato double bass at the start of every two bars to give some emphasis on the bass (an octave lower than the piano).

Then the melody comes in. A wonderful, haunting meditative melody. It wanders a little, but this isn't a problem--the style of this piece lends itself towards that sort of thing. You might want the melody to be this thin, but I think that the piano in octaves, and octave doubling of the melody in piccolo and oboe could give a more mellifluous feel. I'd keep pizzicato double bass every other bar.

The violin rhythm is a little brash, and has a 6/8, barcarole feel to it. This is fine, but I'd put it in a solo line (just mark it with italic text, 'solo', and let your orchestra take care of it--MuseScore playback won't work). Perhaps even put some homophonic chords in the strings beneath, moving with it, all solo, as if a string quintet are playing them, adding to the broad, yet intimate style you've created.

As it goes on, it gets quite interesting; the right hand phrases are 3 or 6 bars in length, whereas the piano accompaniment line is 4. This leads to some interesting harmonic overlaps, which means that although it is slow, there is a pushing, 'Baricades Misterieuses' type background to it.

The clarinet/bassoon part soon just doubles the piano, in the same octave--this just makes the sound larger, and makes them musically superflous. The saxophone can only play one note at a time (as I'm sure you know), so you should separate the notes across voices to show that two players are to perform the chords. I'd also put what is now the bassoon notes into the first quaver beat of the clarinet part. Now the bassoon can play this single note at a lower octave, and give a 'fuller' sound.

Nothing more I'd suggest for the following few bars. The piano line is quite idiomatic of the instrument, bringing Debussy to mind whilst not imitating him. I wouldn't double this line. The 'barcarole' line appears several times, I'd put this in several instruments at octaves each time to draw attention to it.

For the strings section, I'd double the melody in second violins an octave lower. I'd maintain the double basses as pizzicato from earlier. The tuba doubles the double basses--quite a bright sound, I'd mitigate it by also using the bassoons as a mellow tone more suited to this situation. This long conjunct melody I think would lend itself to a countermelody, perhaps. I'll leave that to you.

Just a few thoughts--hopefully they'll be helpful to you. I find it much easier to critique other works than work on my own--just see the poor orchestration on my Battaglia alla Tarantella, for example!

Thank you for sharing such beautiful music with us all. I cannot express enough how great this is.