Thank you so much for such a thorough listen and for taking the time to write this entire comment! Overall I fully agree with all you've said! :)
When we approached working on this project together, we pulled many of our favorite video game space themes and analyzed them, since neither of us have had extensive “space” composition experience. We noticed there were several different styles that all felt like “space” and some of our early ideas (prior to writing the story) were to create tracks in each of these different space sub-categories. Some of them I agree ended up landing really well in this OST while others were a good experimentation, but maybe didn’t hit the mark. I appreciate your comments of track 5 sticking out and I think I agree. This was the first track I made to try and experiment with my sound libraries to try and find a space palette. It was intentionally trying to be poppy since one of the space categories we noticed we called “space pop” and included Rainbow Road themes and several Sonic themes. So the references you picked up were spot on, but I get that it feels like the odd one out of the bunch. This is a great takeaway point from this whole experience! I also really appreciate the mixing notes for the battle track - I hear exactly what you are referring to and totally agree. Great ears! And to be compared to Mario Galaxy is a wonderful compliment. That was a big inspiration for the first two tracks for sure! Thank you once again!