The piano in the first track can feel a little overbearing repeating chords on each beat in the second half
I think overall the mix on the OST could be improved. some songs feel a bit muddy and others feel a bit sharp. A motif or connecting thread between them would also help connect everything nicely.
I like the variation you have in the OST. it makes it feel more complete with the many different sections you have.
Chase reminded me of the music from buckshot roulette.
I liked the instruments you used in the 5th track. they were nice and punchy without being too loud.
Bittersweet end is a really interesting ending song. it feels almost like an incomplete/bad ending song where there is a teaser at the end to say "did you really complete the game though"